Animal Parasites and Messmates
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Title: Animal Parasites and Messmates
Author: P. J. van Beneden
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*** START OF THE PROJECT GUTENBERG EBOOK ANIMAL PARASITES AND MESSMATES ***
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THE INTERNATIONAL SCIENTIFIC SERIES.
ANIMAL PARASITES AND MESSMATES.
BY
P. J. VAN BENEDEN,
PROFESSOR AT THE UNIVERSITY OF LOUVAIN,
CORRESPONDENT OF THE INSTITUTE OF FRANCE.
_WITH EIGHTY-THREE ILLUSTRATIONS._
NEW YORK:
D. APPLETON AND COMPANY,
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1876.
CONTENTS. vii
PAGE
INTRODUCTION.
Adaptation of Food to Animals--Animal Manufacturers--
Brigands--Messmates--Mutualists--Theory of Spontaneous
Generation xiii
CHAPTER I.
ANIMAL MESSMATES.
Definition--Free Messmates--Fixed Messmates 1
CHAPTER II.
FREE MESSMATES.
Found in all Classes--Fierasfers in Holothuridæ--Pilot
Fish--Remora--Crustacean Messmates--Poisoning by
Mussels--Pearl Mussel and small Crab--Dromiæ--Turtle
Crabs--Macrourous Decapods--Hermit Crabs--Friendship of
Pagurus and Anemone--Isopods--Messmates on Whales--
Molluscan Messmates--Lerneans--Distomes--Messmates
of the Echinodermata--Of Sponges--Infusorial Messmates 4
CHAPTER III.
FIXED MESSMATES.
Cirrhipedes--Importance of Embryology--Recurrent
Development--Messmates, characteristic of the various
Species of Whales--Cirrhipedes on Sharks--Crustaceans,
Messmates on other Crustaceans--Cirrhipedes on
Molluscs--Bryozoa--Fossil Messmates--Messmates on
Sponges--Spicules of Hyalonema--Ophiodendrum 53
CHAPTER IV. viii
MUTUALISTS.
Definition--Ricinidæ--Trichodectes of Dog harbouring Larva
of Tænia--Arguli--Caliguli--Ancei--Pranizæ--Cyami--Nematode
Mutualists--Strange form of Histriobdellæ--Egyptian
Distome in Man 68
CHAPTER V.
PARASITES.
Distinction between Parasites and Carnivora--Parasites
found on all Classes of Animals--Males dependent on
Females--Parasites on Man--Abundant Parasites in Stork--
All the Organs nourish Parasites--Different size of
Male and Female--Lerneans--Diplozoa--Migration of
Parasites--Corresponding Changes of Form--Parasites
restricted to certain Regions--Former Theory of
Spontaneous Generation 85
CHAPTER VI.
PARASITES FREE DURING THEIR WHOLE LIFE.
Leeches--Vampires--Cylicobdellæ--Branchellions--Gnats--
Blackflies--Mosquitoes--Gnats in high Latitudes--Tsetse--
Ox-flies--Pteropti--Nycteribiæ--Bugs-- Lice--Fleas--Itch
Insect--Acari on Beetles and Bees--Cheyletus eruditus 107
CHAPTER VII.
PARASITES FREE WHILE YOUNG.
Isopod Parasites--Chigoe--Ticks--Pigeon-mite--Bopyridæ--
Ichthoxenus--Peltogasters--Tracheliastes--Penellæ--
Lerneans--Guinea-worm--Leptodera of Snail--Nematodes in
Bones--Lichnophoræ--Gregarinæ 138
CHAPTER VIII.
PARASITES THAT ARE FREE WHEN OLD.
Utility of Ichneumons--Scoliæ of Tan-beetles--Scolyti of
Seychelles Cocoa-nut Trees--Elms at Brussels destroyed by
Scolyti--Polynema in Eggs of Dragon-fly--Sphex--Platygaster--
Horse-fly--Livingstone--Animals in Paraguay destroyed by ix
Hippobosci--Dipterous Parasites on Sheep and Stag--Gordius--
Shower of Worms--Eels in Ears of Corn 162
CHAPTER IX.
PARASITES THAT MIGRATE AND UNDERGO METAMORPHOSES.
Nostosites--Xenosites--Hosts serving as a Crèche, a
Vehicle, or a Lying-in Hospital--Lamarck on Spontaneous
Generation--Trematodes--Monostomes--Sporocysts and
Cercariæ--Passage from one Host to another--Distomes--
Flukes--Hemistomes--Amphistomes--Tæniæ of the Dog and
Wolf--Hydatids--Tænia solium in Man--Cysticercus of
Pig--Cysticercus of Rabbit and Hare passing into Dog--
Coenurus of Sheep--Bothriocephalus--Linguatula in Negro--
Strongyli--Trichinæ--Panic in Germany--Vibriones in Corn--
Echinorrhynchus--Dicyema 183
CHAPTER X.
PARASITES DURING THEIR WHOLE LIFE.
Strepsitera--Stylops--Rhipiptera--Tristomidæ--Epibdella--
Diplozoon, two Individuals--Polystomum of Frog--Gyrodactyles--
Cochineal Insect--Aphides--Phylloxera of Vine--An Acaris,
its Mortal Enemy--Ant-Cows--Bonnet's Theory of Germs--The
Reduvius personatus, a valuable enemy to the Bed-bug 255
LIST OF ILLUSTRATIONS. x
FIG. PAGE
1.--Ophiodendrum abietinum on Sertularia abietina 66
2.--Ricinus of the Pygarg 72
3.--Caligulus elegans, female: ditto, natural size 73
4.--Different forms of the Bite of a Leech 110
5.--Sucker and jaws 110
6.--Anatomy of Leech 110
7.--Antenna of Gnat 115
8.--Gnat, male and female 118
9, 10.--Lucilia hominivora 120
11.--Ox-fly 121
12.--Antenna of Ox-fly 121
13.--Blue-fly 121
14.--Flesh-fly 122
15.--House-fly 122
16.--Bed-bug 124
17.--Louse 125
18.--Louse--Suckers 126
19.--Ditto--Claw 126
20.--Flea (Pulex irritans) 128
21.--Itch-mite 131
22.--Ditto, female--back view 131
23.--Ditto, male--back view 132
24.--Geographical water-mite 136
25.--Book-mite 137
26.--Chigoe, male 141
27.--Ditto, head 141
28.--Ditto, female 141
29.--Phryxus Rathkei 145
30.--Tracheliastes of Cyprinidæ 149 xi
31.--Lernea branchialis attached to Morrhua luscus 151
32.--Young Guinea-worm, showing Mouth, Tail,
and section of Body 153
33.--Gregarinæ of Nemertes 160
34.--Sac with Psorospermiæ from Sepia officinalis 160
35.--Stylorhynchus Melophagus oligacanthus from Dragon-fly 161
36.--Horse-fly, showing also Anterior and Posterior Extremity 172
37.--Macaco Worm 175
38.--Melophagus of the Sheep 177
39.--Lipoptena of Stag 177
40.--Gordius aquaticus 178
41.--Monostomum verrucosum--Sporocyst with Cercariæ 191
42.--Liver fluke 198
43.--Monostomum mutabile 202
44.--Ditto, ciliated Embryo and young Cercariæ 202
45.--Cercaria of Amphistoma sub-clavatum 203
46.--Sporocyst of Amphistoma sub-clavatum 203
47.--Ditto, from Frog 205
48.--Polystomum integerrimum 205
49.--Cysticercus 206
50.--Vesicular Worm 211
51.--Tape-worm (Tænia solium), showing Scolex and Proglottides 214
52.--Ditto, Rostellum and Suckers 214
53.--Tænia medio-canellata 219
54.--Coenurus of Sheep, and Hydatid 223
55.--Scolex of Tænia echinococcus 226
56.--Tænia echinococcus from the Pig 226
57.--Ditto, from the Dog 227
58.--Bothriocephalus latus 227
59.--Scolex of ditto 227
60.--Egg of ditto 227
61.--Tænia variabilis from Snipe 230
62.--Ditto, more highly magnified 230
63.--Tetrarhynchus appendiculatus from the Plaice 230
64.--Hook of Linguatula 232
65.--Linguatula, showing Hooks 232
66.--Strongylus gigas, female 239
67.--Ascaris lumbricoides; also Head, Tail, and Body 240
68.--Trichocephalus from Man 241
69.--Oxyuris vermicularis, natural size and magnified 241 xii
70.--Trichina, free 243
71.--Trichina encysted in Muscle 243
72.--Echinorhynchus proteus 252
73.--Sac with Psorospermiæ from Sepia officinalis 252
74.--Gregarinæ from Nemertes Gesseriensis 253
75.--Stylorhynchus oligacanthus 253
76.--Dicyema Krohnii from Sepia officinalis 254
77.--Stylops 256
78.--Ditto, with Embryos 257
79.--Larva of Black Stylops 257
80.--Cochineal Insects, male 263
81.--Ditto, female 264
82.--Aphis 264
83.--Rose Aphis, male and female 265
INTRODUCTION. xiii
"The edifice of the world is only sustained by the impulses
of hunger and love."--SCHILLER.
In that great drama which we call Nature, each animal plays its
especial part, and He who has adjusted and regulated everything in its
due order and proportion, watches with as much care over the
preservation of the most repulsive insect, as over the young brood of
the most brilliant bird. Each, as it comes into the world, thoroughly
knows its part, and plays it the better because it is more free to
obey the dictates of its instinct. There presides over this great
drama of life a law as harmonious as that which regulates the
movements of the heavenly bodies; and if death carries off from the
scene every hour myriads of living creatures, each hour life causes
new legions to rise up in order to replace them. It is a whirlwind of
being, a chain without end.
This is now more fully known; whatever the animal may be, whether that
which occupies the highest or the lowest place in the scale of
creation, it consumes water and carbon, and albumen sustains its vital
force.
Therefore, the Hand which has brought the world out of chaos, has xiv
varied the nature of this food; it has proportioned this universal
nourishment to the necessities and the peculiar organization of the
various species which have to derive from it the power of motion and
the continuance of their lives.
The study whose aim is to make us acquainted with the kind of food
adapted to each animal constitutes an interesting branch of Natural
History. The bill of fare of every animal is written beforehand in
indelible characters on each specific type; and these characters are
less difficult for the naturalist to decipher than are palimpsests for
the archæologist.
Under the form of bones or scales, of feathers or shells, they show
themselves in the digestive organs. It is by paying, not domiciliary,
but stomachic visits, that we must be initiated into the details of
this domestic economy. The bill of fare of fossil animals, though
written in characters less distinct and complete, can still be very
frequently read in the substance of their coprolites. We do not
despair even to find some day the fishes and the crustaceans which
were chased by the plesiosaurs and the ichthyosaurs, and to discover
some parasitic worms which had entered with them into the convolutions
of the intestines of the saurians.
Naturalists have not always studied with sufficient care the
correspondence which exists between the animal and its food, although
it supplies the student with information of a very valuable kind. In
fact, every organized body, whether conferva or moss, insect or
mammal, becomes the prey of some animal; every organic substance, sap
or blood, horn or feather, flesh or bone, disappears under the teeth xv
of some one or other of these; and to each kind of _débris_ correspond
the instruments suitable for its assimilation. These primary relations
between living beings and their alimentary regimen call forth the
activity of every species.
We find, on closer examination, more than one analogy between the
animal world and human society; and without much careful scrutiny, we
may say that there is no social position which has not (if I may dare
to use the expression) its counterpart among the lower animals.
The greater part of these live peaceably on the fruit of their labour,
and carry on a trade by which they gain their livelihood; but by the
side of these honest workers we find also some miserable wretches who
cannot do without the assistance of their neighbours, and who
establish themselves, some as _parasites_ in their organs, others
as _uninvited guests_, by the side of the booty which they have
gained.
Some years ago, one of our learned and ingenious colleagues at the
University of Utrecht, Professor Harting, wrote a charming book on the
industry of animals, and demonstrated that almost every trade is known
in the animal kingdom. We find among them miners, masons, carpenters,
paper manufacturers, weavers, and we may even say lace-makers, all of
whom work first for themselves, and afterwards for their progeny. Some
dig the earth, construct and support vaults, clear away useless earth,
and consolidate their works, like miners; others build huts or palaces
according to all the rules of architecture; others know intuitively
all the secrets of the manufacturers of paper, cardboard, woollen
stuffs or lace; and their productions need not fear comparison with xvi
the point-lace of Mechlin or of Brussels. Who has not admired the
ingenious construction of the beehive or of the ant-hill, or the
delicate and marvellous structure of the spider's web? The perfection
of some of these works is so great and so generally appreciated, that
when the astronomer requires for his telescope a slender and delicate
thread, he applies to a living shop, to a simple spider. When the
naturalist wishes to test the comparative excellence of his
microscope, or requires a micrometer for infinitely little objects, he
consults, not a millimetre, divided and subdivided into a hundred or a
thousand parts, but the simple carapace of a diatom, so small and
indistinct that it is necessary to place a hundred of them side by
side to render them visible to the naked eye: and still more, the best
microscopes do not always reveal all the delicacy of the designs which
decorate these Lilliputian frustules. Mons. H. Ph. Adan has lately
shown, with an artist's talent, the infinite beauties which the
microscope reveals in this invisible world.
To whom do the manufacturers of Verviers or of Lyons, of Ghent or of
Manchester, apply for their raw materials? Either to an animal or a
plant; and even up to the present time we have had sufficient modesty
not to have sought to imitate either wool or cotton. Yet these animal
manufacturers carry on their operations every day under our eyes, the
doors wide open to everybody, and none of them is as yet marked with
the trite expression, "No admittance."
"The beau-ideal which we place before us in the arts of spinning and
weaving," said an inhabitant of the South to Michelet, "is the beautiful xvii
hair of a woman: the softest wool, the finest cotton, is very far from
realizing it." The Southerner seemed to forget that this soft wool, as
well as this fine cotton, was not the product of our manufacturers any
more than the woman's hair.
Were these animal machines to sustain injury, or even to be idle for a
certain time, we should be reduced to have nothing wherewith to cover
our shoulders: the fine lady would have neither Cashmere shawl, silk,
nor velvet in her wardrobe; we should have neither flannel nor cloth
to make our clothes; the herdsman even would not have his goat's skin
to protect him from the inclemency of the season. Thanks to the animal
which gives us his flesh and his fleece, we are able to leave the
southern regions, to brave the rigour of other climes, and establish
ourselves side by side with the reindeer and the narwhal, in the midst
of eternal snow.
We have our science and our steam-engines, of which we are justly
proud; the animals have only their simple instinct to enable them to
fabricate their marvellous tissues, and yet they succeed better than
ourselves. The so-called blind forces of nature produce thread, the
use of which the genius of man seeks in vain to supersede; and we do
not even dream of entering into competition with these living machines
which we daily crush under our feet.
All these occupations are openly carried on; and if there are some
which are honest, it may be said that there are others which deserve
another character. In the ancient as well as the new world, more than
one animal resembles somewhat the sharper leading the life of a great
nobleman; and it is not rare to find, by the side of the humble xviii
pickpocket, the audacious brigand of the high road, who lives solely
on blood and carnage. A great proportion of these creatures always
escape, either by cunning, by audacity, or by superior villainy, from
social retribution.
But side by side with these independent existences, there are a
certain number which, without being parasites, cannot live without
assistance, and which demand from their neighbours, sometimes only a
resting-place in order to fish by their side, sometimes a place at
their table, that they may partake with them of their daily food; we
find some every day which used to be considered parasites, yet which
by no means live at the expense of their hosts.
When a copepod crustacean instals himself in the pantry of an
ascidian, and filches from him some dainty morsel, as it passes by;
when a benevolent animal renders some service to his neighbour, either
by keeping his back clean, or removing detritus which clogs certain
organs, this crustacean or this animal is no more a parasite than is
he who cowers by the side of a vigilant and skilful neighbour, quietly
takes his siesta, and is contented with the fragments which fall from
the jaws of his companion. We may say the same thing of the fish
which, through idleness, attaches itself, like the remora, to a
neighbour who swims well, and fishes by his side without fatiguing his
own fins.
The services of many of these are rewarded either in protection or in
kind, and _mutuality_ can well be exercised at the same time as
_hospitality_.
Those creatures which merit the name of parasites feed at the expense
of a neighbour, either establishing themselves voluntarily in his xix
organs, or quitting him after each meal, like the leech or the flea.
But when the larva of an ichneumon devours, organ after organ, the
caterpillar which serves him as a nurse, and at last eats her
entirely, can we call him a parasite? According to Lepelletier de
Saint-Fargeau, who has so successfully treated these questions, the
parasite is he who lives at the expense of another, eating that which
belongs to him, but not devouring his nurse herself. Nor is the
ichneumon a carnivorous animal, for the true beast of prey cares
nothing at any period of his existence for the life of his victim.
True parasites are very commonly found in nature, and we should be
wrong were we to consider that they all live a sad and monotonous
life. Some among them are so active and vigilant that they sustain
themselves during the greater part of their life, and only seek for
assistance at certain determinate periods. They are not, as has been
supposed, exceptional and strange beings, without any other organs
than those of self-preservation. There is not, as was formerly
supposed, a _class_ of parasites, but all the classes of the
animal kingdom include some among their inferior ranks.
We may divide them into different categories.
In the first of these we will place together all those which are free
at the commencement of their life, which swim and take their sport
without seeking assistance from others, until the infirmities of age
compel them to retire into a place of refuge. They live at first like
true Bohemians, and are certain of getting invalided at last in some
well-arranged asylum. Sometimes both the male and female require this
assistance at a certain age; with others it is the female only, as the xx
male continues his wandering life. In some cases, the female carries
her partner with her, and supports him entirely during his captivity;
her host nourishes her, and she in her turn feeds her husband. We find
few female gill-suckers which have not with them their Lilliputian
males, which, like a shadow, never quit them. But we also find males,
living as parasites of their females, among those curious crustaceans
known by the name of cirrhipeds. All the parasitical crustaceans are
placed in this first category.
We find others, the ichneumons for example, which are perfectly at
liberty in their old age, but require protection while young. There
are many of these, which as soon as they escape from the egg, are
literally put out to nurse; but from the day when they cast off their
larval robe, they are no longer under restraint, but, armed cap-à-pie,
they rush eagerly in quest of adventure, and die like others on the
high road. In this category are generally found parasitical
hymenopterous and dipterous insects.
Other kinds are lodgers all their lives, though they change their
hosts, not to say their establishment, accordingly to their age and
constitution. As soon as they quit the egg, they seek for the favours
of others, and all their itinerary is rigorously traced out for them
beforehand. Fortunately we are at present acquainted with the
halting-places and magazines of a great number of those which belong
to the order of cestode and trematode worms. These flat and soft worms
begin life usually as vagabonds, aided by a ciliary robe which serves
as an apparatus for locomotion; but scarcely have they tried to use xxi
their delicate oars, before they demand assistance, lodge themselves
in the body of the first host that they meet, whom they abandon for
another living lair, and then condemn themselves to perpetual
seclusion.
That which adds to the interest inspired by these feeble and timid
beings is, that at each change of abode, they change also their
costume; and that when they have reached the limit of their
peregrinations, they assume the virile toga--we had almost said, the
wedding robe. The sexes appear only under this later envelope; up to
this period they have had no thoughts of the cares of a family. It has
always been somewhat difficult to establish the identity of those
persons who frequent the public saloons one day, and are found on the
next in the most obscure haunts, dressed as mendicants. Most of the
worms which have the form of a leaf or a tape give themselves up to
these peregrinations, and those which do not arrive at their last
stage, die usually without posterity.
It is interesting to remark that these parasitical worms do not
inhabit the various organs of their neighbours indiscriminately, but
all begin their life modestly in an almost inaccessible attic, and end
it in large and spacious apartments. At their first appearance they
think only of themselves, and are contented to lodge, as
_scolices_ or vesicular worms, in the connective tissue of the
muscles, of the heart, of the lobes of the brain, or even in the ball
of the eye; at a later stage, they think of the cares of a family, and
occupy large vessels like the digestive or respiratory passages, always
in free communication with the exterior; they have a horror of being xxii
enclosed, and the propagation of their species requires access to the
outer air.
In the last category are found those which need assistance all their
lives; as soon as they have penetrated into the body of their host,
they never remove again, and the lodging which they have chosen serves
them both as a cradle and a tomb.
Some years since, no one suspected that a parasite could live in any
other animal than that in which it was discovered. All helminthologists,
with few exceptions, looked upon worms in the interior of the body as
formed without parents in the same organs which they occupy. Worms
which are parasites of fish, had been seen a long time before this in
the intestines of various birds: experiments had even been made to
satisfy observers of the possibility of these creatures passing from
one body to another; but all these experiments had only given a
negative result, and the idea of inevitable transmigration was so
completely unknown that Bremser, the first helminthologist of his age,
raised the cry of heresy, when Rudolphi spoke of the ligulæ of fishes
which could continue to live in birds.
At a period nearer to our own times, our learned friend, Von Siebold,
deservedly called the prince of helminthologists, was entirely of this
opinion, and compared the cysticercus of the mouse with the tape-worm
of the cat, considering this young worm as a wandering, sick, and
dropsical being.
In his opinion, the worm had lost its way in the mouse, as the tænia
of the cat could live only in the cat. Flourens considered it a
romance when I myself announced to the "Institut de France," that
cestode worms must _necessarily_ pass from one animal to another xxiii
in order to complete the phases of their evolution.
At the present time, experiments respecting these transmigrations are
repeated every day in the laboratories of zoology with the same
success; and Mons. R. Leuckart, who directs with so much talent the
Institute of Leipzig, has discovered, in concert with his pupil
Mecznikow, transmigrations of worms accompanied by changes of sex;
that is to say, they have seen nematodes, the parasites of the lungs
of the frog, always female or hermaphrodite, produce individuals of
the two sexes which do not resemble their mother, and whose habitual
abode is not in the lungs of the frog but in damp earth. In other
words, let us imagine a mother, born a widow, who cannot exist without
the assistance of others, producing boys and girls able to provide for
themselves. The mother is parasitical and viviparous, her daughters
are, during their whole life, free and oviparous.
This observation leads us to another sexual singularity, lately
observed, of males and females of different kinds in one and the same
species, and which give birth to progeny which do not resemble each
other; the same animals, or rather the same species, proceed from two
different eggs fecundated by different spermatozoids.
Now that these transmigrations are perfectly known and admitted, the
starting-point of the inquiry has been so entirely forgotten that the
honour of the discovery has been frequently attributed to
fellow-workers, who had no knowledge of it till the demonstration had
been completed, and the new interpretation generally accepted. But let
us return to our subject.
The assistance rendered by animals to each other is as varied as that xxiv
which is found amongst men. Some receive merely an abode, others
nourishment, others again food and shelter; we find a perfect system
of board and lodging combined with philozoic institutions arranged in
the most perfect manner. But if we see by the side of these paupers,
some which render to one another mutual services, it would be but
little flattering to them to call all indiscriminately either
parasites or messmates (_commensaux_). We think that we should be more
just to them if we designated the latter kinds _mutualists_, and thus
_mutuality_ will take its place by the side of _mess-table_
arrangements (_commensalism_) and of parasitism.
It would also be necessary to coin another name for those which, like
certain crustaceans, or even some birds, are rather guests which
_smell out a feast from afar_ (pique-assiettes) than parasites;
and for others which repay by an ill turn the assistance which they
have received. And what name shall we give to those which, like the
plover, render services which may be compared to medical attendance?
This bird in fact performs the office of dentist to the crocodile. A
small species of toad acts as an accoucheur to his female companion,
making use of his fingers as a forceps to bring the eggs into the
world. Again, the pique-boeuf performs a surgical operation, each
time that he opens with his lancet the tumour which encloses a larva
in the midst of the buffalo's back. Nearer home, we see the starling
render in our own meadows the same service as the pique-boeuf
(_Buphaga_) in Africa; and we may see that among these living
creatures there is more than one speciality in the healing art.
We must not forget that the occupation of a gravedigger is equally xxv
general in nature, and that it is never without some profit to himself
or his progeny that this gloomy workman inters the bodies of the dead.
Certain animals have an occupation analogous to that of the shoeblack
or the scourer, and they freshen up with care, and even with a kind of
coquettish pleasure, the toilet of their neighbours.
And how must we designate the birds known by the name of stercorariæ,
which take advantage of the cowardice of sea-gulls in order to live in
idleness? It is useless for the gulls to trust to the strength of
their wings, the stercorariæ in the end compel them to disgorge their
food in order that they may partake of the spoils of their fishery.
When followed up too closely, these timid birds throw up the contents
of their crop, to render themselves lighter, like the smuggler who
finds no means of safety except in abandoning his load.
We must not, however, be too hard upon all this class, since very
often, as in the case of the gnat, it is only one of the sexes which
seeks a victim.
All animals usually live for the passing day; and yet there are some
which practise economy, which are not ignorant of the advantages of
the savings bank, and, like the raven and the magpie, think of the
morrow, to lay up in store the superfluity of the day's provision.
As we have before said, this little world is not always easy to be
known, and in its societies, to which each brings his capital, some in
activity, others in violence or in stratagem, we find more than one
_Robert Macaire_ who contributes nothing, and takes advantage of
all. Every species of animal may have its parasites and its messmates,
and each may perhaps have some of different sorts, and in diverse xxvi
categories.
But whence come those disgusting beings, whose name alone inspires us
with horror, and which instal themselves without ceremony, not in our
dwellings, but in our organs, and which we find it more difficult to
expel than rats or mice? They all derive their existence from their
parents.
The time has passed when a vitiated condition of the humours, or the
deterioration of the parenchyma was considered a sufficient cause for
the formation of parasites, and when their presence was regarded as an
extraordinary phenomenon resulting from the morbid dispositions of the
organism. We have reason to hope that this language will, during the
next generation, have entirely disappeared from works on physiology
and pathology. Neither the temperament nor the humours have any
influence on parasites, and they are not more abundant in delicate
individuals than in those who enjoy the most robust health. On the
contrary, all wild animals harbour their parasitical worms, and the
greater part of them have not lived long in captivity, before nematode
and cestode worms completely disappear. It is only the imprisoned
parasites which do not desert them.
All these mutual adaptations are pre-arranged, and as far as we are
concerned, we cannot divest ourselves of the idea that the earth has
been prepared successively for plants, animals, and man. When God
first elaborated matter, He had evidently that being in view who was
intended at some future day to raise his thoughts to Him, and do Him
homage.
This is the answer which I would give to the question recently xxvii
propounded by Mons. L. Agassiz. "Were the physical changes to which
our globe has been subjected effected for the sake of the animal
world, considered in its relations from the very beginning, or are the
modifications of animals the result of physical changes?" in other
words, has the earth been made and prepared for living beings, or have
living beings been as highly developed as was possible, according to
the physical vicissitudes of the planet which they inhabit?
This question has always been discussed, and that science which cannot
look beyond its scalpel, will never succeed in resolving it. Each one
must seek by his own reason the solution of the great problem.
When we see the newly-born colt eagerly seeking for its mother's
teats, the chick as soon as it is hatched beginning to peck, or the
duckling seeking its puddle of water, can we recognize anything but
instinct as the cause of these actions, and is not this instinct the
libretto written by Him who has forgotten nothing?
The statuary who tempers the clay from which to make his model, has
already conceived in his mind the statue which he is about to produce.
Thus it is with the Supreme Artist. His plan for all eternity is
present to His thought. He will execute the work in one day, or in a
thousand ages. Time is nothing to Him; the work is conceived, it is
created, and each of its parts is only the realization of the creative
thought, and its predetermined development in time and space.
"The more we advance in the study of nature," says Oswald Heer in "Le
Monde primitif" which he has just published, "the more profound also
is our conviction, that belief in an Almighty Creator and a Divine xxviii
Wisdom, who has created the heavens and the earth according to an
eternal and preconceived plan, can alone resolve the enigmas of
nature, as well as those of human life. Let us still erect statues to
men who have been useful to their fellow-creatures, and have
distinguished themselves by their genius, but let us not forget what
we owe to Him who has placed marvels in each grain of sand, a world in
every drop of water."
At first we shall treat of animal _messmates_, secondly of _mutualists_,
and thirdly of parasites.
_ANIMAL PARASITES_ 1
_AND MESSMATES_.
CHAPTER I.
ANIMAL MESSMATES.
The messmate is he who is received at the table of his neighbour to
partake with him of the produce of his day's fishing; it would be
necessary to coin a name to designate him who only requires from his
neighbour a simple place on board his vessel, and does not ask to
partake of his provisions.
The messmate does not live at the expense of his host; all that he
desires is a home or his friend's superfluities. The parasite instals
himself either temporarily or definitively in the house of his
neighbour; either with his consent or by force, he demands from him
his living, and very often his lodging.
But the precise limit at which commensalism begins is not always
easily to be ascertained. There are animals which live as messmates
with others only at a certain period of their lives, and which provide
for their own support at other times; others are only messmates under
certain given circumstances, and do not usually merit this 2
appellation.
In the higher animals, this relation between them is generally well
known, and justly appreciated, but it is not the same in the inferior
ranks; and more than one animal may pass for a messmate or a parasite,
for a robber or for a mendicant, according to the circumstances under
which he is observed. The sharper passes for an honest man as long as
he has not been taken _in flagrante delicto_. Thus, in order to
be just, we must carefully examine the indictment, and not pronounce
sentence without strict examination.
The greater part of those animals which have established themselves on
each other, and live together on a good understanding and without
injury, are wrongly classed as parasites by the generality of
naturalists. Now that the mutual relations of many of these are better
understood, we know many animals which unite together to render each
other mutual assistance; while there are others which live like
paupers on the crumbs which fall from the rich man's table. There are
many relations between the different species which can be discovered
only after minute examination, but which have recently been
appreciated with greater impartiality.
Animal messmates are rather numerous, and commensalism has been
observed, not only in animals of the present age, but in those of the
primary epoch. Wyville Thomson explained to me, while I was myself his
messmate at Edinburgh, at the meeting of the British Association in
1871, that the polyps of the Silurian age already practised it. We do
not class among animal messmates those living creatures which, like
the birds which we keep in cages, charm the ear with their song, or
which, in spite of our care, live at the expense of our pantry; we 3
will only refer to veritable messmates, which, sometimes through
weakness of constitution, sometimes for want of activity, can neither
feed themselves nor bring up their family without seeking help from
their neighbours.
There are some free messmates which never renounce their independence,
whatever may be the advantages which their Amphitryon enjoys; they
break their alliance with him for the slightest motive of discontent,
and go and seek their fortune elsewhere. Their susceptibility or their
love of change guides them. They are recognized by their fishing
implements or their travelling gear, which they never lay aside. These
free messmates are the more numerous. The others, the fixed messmates,
instal themselves with a neighbour, and live at their ease, having
completely changed their dress, and renounced for ever an independent
life. Their fate is thenceforward bound to him who carries them.
Under these two categories we shall cite several examples, and glance
at the differences which the various classes of the animal kingdom
present in this respect, beginning with the higher ranks.
CHAPTER II. 4
FREE MESSMATES.
We meet with free messmates in various classes of the animal kingdom.
They sometimes mount on the back of a neighbour, sometimes occupy the
opening of the mouth, the digestive passages, or the exit for the
excreta; at times they place themselves under the shelter of the cloak
of their host, from whom they receive both aid and protection.
Among the vertebrates, there are few except fishes which merit a place
here; it is only amongst these that we meet with species at the mercy
of others, and dependent on acolytes, which are in every respect
inferior to themselves.
An interesting messmate belonging to this first category is a fish of
graceful form, named donzelina, which goes to seek its fortune in the
body of a holothuria. Naturalists have long known it under the name of
Fierasfer. It has a long body like that of an eel, entirely covered
with small scales; and as it is quite compressed, it has been compared
to the sword which conjurors thrust into their oesophagus. They are
found in different seas, and all have similar habits. This fish is
lodged in the digestive tube of his companion, and, without any 5
regard for the hospitality which he receives, he seizes on his portion
of all that enters. The Fierasfer contrives to cause himself to be
served by a neighbour better provided than himself with the means of
fishing.
Dr. Greef, at present Professor at Marbourg, found at Madeira a
holothuria of a foot in length, in which a vigorous Fierasfer lived in
peace. Quoy and Gaimard, in the account of their voyage round the
world, have remarked long since, that the _Fierasfer hornei_ is
found in the _Stichopus tuberculosus_.
The holothuriæ seem to exist under very advantageous conditions in
this respect, since we see Fierasfers, which are themselves tolerable
gluttons, accompanied by Palæmons and Pinnotheres in the same animal.
Professor C. Semper has seen holothuriæ in the Philippine Islands
which bore a considerable resemblance, in this respect, to an hotel
with its table d'hôte.
These singular fishes have been long noticed, but it was not till
recently that their presence in a host so low in the scale as a
holothurian could be explained.
But if naturalists are agreed as to the bond which unites these fishes
to the holothuriæ, they do not agree as to the organs which they
inhabit in their living hotel. Do they lodge in the digestive cavity
of the holothuriæ, or do they inhabit the arborescent respiratory
processes which open at the posterior extremity of the body? Until
recently it was thought that it was in their stomach, but a doubt has
arisen. Professor Semper, who has studied these animals with
particular care at the Philippine Islands, had the curiosity to open
the stomach of some of them, and found there, not the animals taken by 6
the holothuriæ, but the remains of its respiratory processess which
they were in the act of digesting. Is it then merely a messmate? We
must have more information on this point; and if it were not
accidentally that the fierasfer swallowed the walls of the compartment
in which he was lodged, he ought rather to take his place among
parasites. Though it lodges in the respiratory processes, as the
learned professor at Wurtzburg asserts, the fierasfer may also be a
messmate after the fashion of so many others which inhabit the
neighbourhood of the rectum, in order the more conveniently to snap up
those animals which are attracted by the odour.
The fierasfers are not the only fishes which seek assistance from the
holothuriæ; a species lives at Zamboanga, to which the specific name
of Scabra has been given, and in the stomach of which, says Mons.
Johannes Müller, usually lives a myxinoid fish, called _Enchelyophis
vermicularis_. Unfortunately, we are not told in what part of the
stomach it resides; for all is stomach in these animals.
It is less degrading for a fish to ask assistance from one in his own
rank. The Mediterranean offers a curious instance of this. Risso saw
at Nice, at the commencement of this century, the monstrous fish known
under the name of _Beaudroie_ (the angler, or fishing-frog)
lodging in its enormous branchial sac a fish of the family of the
Murenidæ, the _Apterychtus ocellatus_. He is found there
evidently under the condition of a messmate. Although the eels
generally get their living easily, the Angler possesses fishing
implements which are wanting in them, and when both of them are 7
immersed in the ooze, it carries on a fishery sufficiently abundant to
enable it to share the spoil with others. This same angler lives in
the northern seas, and there it harbours an amphipod crustacean, which
until lately has escaped the vigilance of carcinologists. We shall
speak of it further on.
Dr. Collingwood saw a sea anemone in the Chinese Sea, which was not
less than two feet in diameter, and in the interior of which lodges a
very frisky little fish, the name of which he could not tell.
Lieut. de Crispigny has observed a sea anemone (_Actinia
crassicornis_) living on good terms with a malacopterygian fish, the
_Premnas biaculeatus_. This fish penetrates into the interior of the
anemone; the tentacles close round it, and it lives thus for a
considerable time enclosed as in a living tomb. Mons. de Crispigny has
kept these animals alive for more than a year, in order to make
careful observations on them. A fish known by the name of _Oxybeles
lumbricoides_ has been also found in the Indian Seas, which modestly
takes up his quarters in a star-fish (_Asterias discoida_). Another
case of _commensalism_ has been made known to us by Professor
Reinhardt of Copenhagen. A siluroid of Brazil, of the genus
_Platystoma_, a skilful fisherman, thanks to his numerous barbules,
lodges in the cavity of his mouth some very small fishes, which were
for a long time considered as young siluroids; it was supposed that
the mother brought her progeny to maturity in the cavity of the mouth,
as marsupials do in the abdominal pouch, or as some other fishes do.
These messmates are perfectly developed and adult, but instead of
living on the produce of their own labour, they prefer to instal
themselves in the mouth of an obliging neighbour, and to take their 8
tithes of the succulent morsels which he swallows. This little fish
has received the name of _Stegophilus insidiatus_. We see that in the
animal world it is not always the great which take advantage of the
little. Still, let us not be deceived; there are fishes in the
latitude of the Island of Ceylon which really hatch their eggs in the
cavity of the mouth, and we have seen some in the museum at Edinburgh,
labelled with the name of _Arius bookei_. Louis Agassiz has made the
same observation on a fish of the Amazon, which has also been
recognised by Jeffreys Wyman. One fish wraps up its eggs in the
fringes of its branchiæ, and protects them till they are hatched;
another lays its eggs in holes hollowed out by itself in the steep
banks of the river, and protects the young ones after they are hatched.
To hatch the eggs in the mouth is not more extraordinary than to hatch
them in any other part of the body. The _Sygnathidæ_ hatch theirs
in a pouch behind the anus; and it is a curious circumstance that the
females do not undertake this duty. The males alone carry their
progeny with them. This recalls to our recollection that curious
example of the birds known under the name of _Phalaropes_, among
which the males only hatch the eggs. The female of the cuckoo abandons
her eggs, and entrusts them to the female of another bird.
The cuckoo suggests to us the mound-making Megapode and the Talegalla
of Latham, both of which inhabit Australia; these birds deposit their
eggs in an enormous mass of leaves or grass, which grows warm by
decomposition, and the temperature of which is great enough to hatch
them. The young ones when they come out of the egg are sufficiently 9
developed to be able to provide for their own wants, and to do without
a mother's care.
To return to our animal messmates: let us notice the result of the
observations of a learned and skilful naturalist who has rendered
great services to ichthyology. Dr. Bleeker has described a still more
remarkable association in the Indian seas; it is that of a crustacean,
the _Cymothoa_, taking advantage of a fish known under the name
of _Stromatea_; too imperfectly organized to fish for itself at
large, but more skilful in snapping up all that comes within its
reach, it makes its home in the buccal cavity of the Stromatea.
But of all crustaceans, the most cruel is the isopod named
_Ichthyoxena_, which hollows out for itself and its female a
large dwelling-place in the coats of the stomach of a cyprinoid fish.
We will return again to these examples.
The _Physaliæ_, those charming living nosegays of the tropical
regions, also give lodging in their cavities, and in the midst of
their long cirrhi, to little adult and perfect fishes, belonging to
the family of the _Scombridæ_, a family to which are attached the
tunny and the mackerel. These sea-butterflies flutter away their
indolent existence at the expense of their host. Voyagers tell us that
they have seen them by dozens concealed in these animated festoons.
Mons. Al. Agassiz has mentioned, in his illustrated catalogue, another
fact, quite as extraordinary, observed in the Bay of Nantucket, in the
United States; it relates to a nocturnal Pelagia (_Dactylometra
quinquecirra_, Ag.) always accompanied, not to say escorted, by a
species of herring. The two neighbours constitute together an 10
association which probably redounds to the advantage of both.
Without quitting our own sea-coast, we find an association of the same
kind between young fishes (_Caranx trachurus_) and a beautiful medusa
(_Chrysaora isocela_). This sea nettle often encloses several young
specimens of Caranx, which we are surprised to see issuing full of
life from the transparent bodies of these polyps. Indeed, it is not
rare to find other fishes in the medusæ. Dr. Gunther, who has arranged
with so much care the rich collection of fishes in the British Museum,
has shown us some specimens of the _Labrax lupus_, and of the
_Gasterosteus_, which had been obtained from the interior of different
medusæ; and these associations have been also remarked by various
distinguished observers, among whom we may mention Messrs. Sars, Rud.
Leuckart, and Peach. The captain of the frigate _Jouan_, when in the
Indian Sea, on October 26th, 1871, in 13° 20' N. lat., and 60° 30' E.
long., that is to say, about 200 leagues to the west of the Laccadive
Islands, saw, in very fine weather, the sea, which was at that time
very calm, covered with medusæ, and the greater part of these were
escorted by many little fishes of the genus _Ostracion_, the species
of which he was unable to ascertain. It is probable that the school of
medusæ set in motion certain animals which are eagerly sought after by
the Ostracions.
The Pilot is a fish of which much has been recorded; fishing for it is
one of the principal recreations of sailors during their long voyages.
Some assure us that it snaps off the bait, without touching the
murderous hook which threatens the shark; and as it never quits its
companion, others have supposed that it lives on the morsels 11
abandoned by it. Neither of these suppositions is correct; and as the
shark does not need its services to point out the danger, we must
content ourselves with mentioning this curious association without
endeavouring to explain it.
In fact, we have had the opportunity of examining many well-preserved
specimens, the stomach of which contained potato parings, the
carapaces of crustaceans, the _débris_ of fishes, marine plants
(fuci), and a piece of _cut_ fish, which had evidently served as
a bait. The pilot does not, therefore, live on the leavings of his
companion, but on his own industry, and doubtless finds some advantage
in piloting his neighbour. Through the great kindness of Dr. Gunther
we have been able to make this interesting examination in the rich
galleries of the British Museum. We desire to take this opportunity of
expressing our gratitude to this learned man and to his illustrious
colleagues, who have the direction of that vast establishment, which
is ever open to those who labour for the advancement of science.
The pilot has sometimes been confounded with a very different fish,
which does not merely remain in the neighbourhood of the shark, but
establishes itself upon him, and moors himself to him by the aid of a
particular apparatus, for a longer or shorter time; we may even say
during the whole of the voyage. This is the Remora.
Is this fish the messmate of the shark to which he is attached? As in
the case of the pilot, an examination alone could decide the question.
We have opened at the British Museum the stomachs of several remoras
of different sizes, and we have been able to ascertain that they also
fish on their own account; their food was composed of morsels of 12
fish which had served as bait, of young fish swallowed whole, and of
some remains of crustacea. The remora is simply anchored to his host,
and asks from him nothing but his passage. He is contented, like the
pilot, to fish in the same waters as the shark which transports him.
Sailors, even now, are convinced that if any one of these remoras
should attach itself to the ship, no human power could cause it to
advance, and that it must of necessity stop. It is certain that the
fishermen of the Mozambique Channel take advantage of this faculty, to
fish for turtles and certain large fish. They pass through the tail of
the remora a ring to which a cord is attached, and then send it in
pursuit of the first passer-by which they consider worthy to be
caught. This kind of fishing resembles in some degree the sport of
hawking with falcons.
So extraordinary a being could not fail to attract the attention of
those among the ancients who were students of nature. Pliny assures us
that the remora was used in the preparation of a philtre capable of
extinguishing the flames of love.
There must be many free animal messmates among insects, and
entomologists should make them known; for example, many of them live
with ants, as the _Pselaphidæ_ and _Staphylinidæ_. Certain
hairs of these insects, it is said, secrete a sweet liquid of which
ants partake greedily. If we may believe a skilful observer, Mons.
Lespès, there are some among them, as the Clavigers, which in exchange
for the services which they render are fed by the ants themselves. We
may also mention the larvæ of the _Meloë_, which seem to live as
parasites, and the true nature of which was so long unknown.
The females of the _Meloë_ lay their eggs near the ranunculus and 13
other plants whose flowers are regularly visited by bees. After these
are hatched, the larvæ ascend into the flowers and wait patiently till
a bee takes them on his back, and carries them into the interior of
the hive. This insect was formerly known under the name of the
bee-louse, but this appellation is improper, for the bee is not the
host of the meloë, but simply its beast of burden. According to recent
observations, flies perform the same office for _Chelifers_, and
certain aquatic and land coleoptera for several kinds of acaridæ.
In the class of animal messmates we find also a coleopterous insect
that lodges in a manner similar to the paguri, of which we shall
presently speak. The female of the _Drilus_, a species allied to
glowworms, attacks the snail, and when it has devoured it, instals
itself in the shell, to pass through its metamorphoses; when
necessary, it frequently changes its shell and chooses successively
more spacious lodgings. Like a true Sybarite, the drilus weaves a
curtain of tapestry before the entrance of its habitation, and remains
there peaceably surrounded by the vestment of its youth.
Remarkable examples of free messmates are found more especially among
crustaceans. It is well known that this class includes lobsters,
crabs, prawns, and those legions of small animals which serve as the
police of the sea-shore, purifying the waters of the ocean of all
organic matters, which otherwise would corrupt them. They do not, like
insects, shine with variegated colours; their forms are hardy and
varied, and they are often pleasing on account of the singularity of
their movements. Professor Verrill has recently studied some of 14
these creatures, and has clearly shown how interesting they are, not
only to naturalists, but to people in general.
Crustaceans and worms furnish the greatest number of paupers and
infirm individuals; and a great many of them need the continual
assistance of their neighbours to enable them to get their living.
While other animals advance towards perfection as they grow older, it
is far different with many crustaceans, and we should be tempted to
refer to the vegetable kingdom many of them at the very period when
they are approaching the adult condition. Cuvier placed all the class
of cirrhipedes among the mollusca, and the lernæans among the worms.
Many of these animals which are but indifferently adapted to live
without help from others, have recourse to benevolent neighbours; from
one they seek only shelter, from another a part of his booty, from a
third both an asylum and protection. They are often reduced to a mere
skin; everything else has disappeared, and there remains no proper
organ except that which is necessary for the reproduction of the
species. Corpulent, blind, impotent, legless cripples, their existence
is more precarious than that of those miserable mutilated beings found
in our cities; they only live on the blood of the neighbour which
gives them an asylum. Yet when they first quit the egg they are all
free; they frisk, they swim with the rapidity of lightning, and at the
close of life we find them deformed, and crouched in some living
refuge, as if a foul leprosy had atrophied within them all the organs
which served as a means of communication with the outer world.
Parasites and messmates, furnished at first with the same kind of
limbs and the same habits, can sometimes only be distinguished from 15
each other when we have made our observations on them in their first
swaddling clothes. The child has given a clue to the history of the
old man.
We will not examine these animals in all the details of their private
life, and yet we are strongly tempted to confess to our readers some
of the indiscreet acts of which we have been guilty, in watching them
while changing their dress. Notwithstanding their shyness and their
desire to escape observation during the moulting period, we have more
than once made observations on them while quitting their garment which
has become too small. The old tunic generally splits down the back,
and falls off all in one piece as it gives the animal egress. The
crustacean is extended quite soft and supple by the side of its rigid
carapace.
Of all the free crustacean messmates, one of the most interesting,
though among the smallest of them, is a tiny crab, about as large as a
young spider, which lives in mussels, and which has been often
accused, though evidently wrongfully, as the cause of the
indisposition so well known by those who are fond of this mollusc.
Very many of them have been seen within the last few years, and yet
accidents have been very few. The mussels themselves are guilty; they
produce on some persons an injurious effect, through _idiosyncracy_.
We have at least a word to serve as an explanation, and at present we
must content ourselves with it.
Under what conditions do those crabs, called by naturalists
Pinnotheres, and which we do not find elsewhere, inhabit mussels? Are
they parasites, pseudo-parasites, or messmates? It is not a taste for
voyaging which tempts them, but the desire of having always a secure 16
retreat in every place. The pinnothere is a brigand who causes himself
to be followed by the cavern which he inhabits, and which opens only
at a well-known watchword. The association redounds to the advantage
of both; the remains of food which the pinnothere abandons are seized
upon by the mollusc. It is the rich man who instals himself in the
dwelling of the poor, and causes him to participate in all the
advantages of his position. The pinnotheres are, in our opinion, true
messmates. They take their food in the same waters as their
fellow-lodger, and the crumbs of the rapacious crabs are doubtless not
lost in the mouth of the peaceful mussel. There is no doubt that these
little plunderers are good lodgers, and if the mussels furnish them
with an excellent hiding-place and a safe lodging, they themselves
profit largely by the leavings of the feast which fall from their
pincers. Little as they are, these crabs are well furnished with
tackle, and advantageously placed to carry on their fishery in every
season. Concealed in the bottom of their living dwelling-place (a den
which the mussel transports at will) they choose admirably the moment
and the place to rush out to the attack, and always fall on their
enemy unawares. Some of these pinnotheres live in all seas, and
inhabit a great number of bivalve molluscs. The northern seas contain
a large species of Modiola (_Modiola Papuana_) which is especially
found in deep and almost inaccessible parts, and which always encloses
a couple of pinnotheres about the size of a hazel-nut. We have opened
hundreds of these modiolæ, and we have never met with any without
their crabs. We have long since deposited some specimens of these 17
pinnotheres in the galleries of the Natural History Museum at Paris.
The large mussel, which furnishes fine pearls (_Avicula
margaritifera_), lodges also pinnotheres of a particular species by
the side of another messmate more allied to a lobster than a crab. It
is not even impossible that these crustaceans, with other messmates or
parasites, contribute to the formation of pearls, since these gems, so
highly prized in the fashionable world, are only the result of
vitiated secretions, and are usually the result of wounds.
We also meet with a little crab (_Ostracotheres tridacnæ_, Ruppel) in
the acephalous mollusc, whose immense shell sometimes serves as a
vessel for holy water; and it lives doubtless in many other bivalves
which have not yet been examined.
Dr. Léon Vaillant has written a very interesting memoir on the
Tridacnæ, and informs us that the crab takes shelter in their
branchial chamber. Therefore, since the molluscs live only on
vegetable substances, while the Ostracotheres feed entirely on animal
matter, Mons. Vaillant supposes that the latter take their choice of
the food as it enters, and seize on its passage that which suits them
best. Mr. Peters, during his abode on the coast of Mozambique, studied
a great many of these acephala and pearl-mussels, and found their
interior inhabited by three crustacean decapods, a pinnothere, and two
macrouræ allied to the _Pontonia_, to which he has given the name of
_Conchodytes_; the _Conchodytes tridacnæ_ inhabits the _Tridacna
squamosa_; the _Conchodytes meleagrinæ_, as its specific name
indicates, lives in the shell of the pearl-mussel.
Professor Semper has recently observed pinnotheres in holothurians at 18
the Philippine Isles, and Mons. Alphonse M. Edwards has described some
from New Caledonia (_P. Fischerii_); so that these little crabs,
the friends of the molluscs, are known in both hemispheres.
Do not these conditions seem to authorize the conclusion that the same
thought has presided over the appearance of all living creatures; that
they have all come into existence, not according to the chance
arrangement of surrounding media, but according to the laws
established from the very origin of all things?
The shell which lodges both these pinnotheres, in the Mediterranean as
well as the Atlantic, is a large acephalous mollusc, known under the
name of _Jambonneau_ (a small ham or gammon), and which, according to
Aristotle, harbours two different kinds of messmates. This illustrious
natural philosopher also described a Pontonia (_Pontonia custos_,
Guérin--_P. Pyrrhena_, M. Edw.) about an inch and a half long, of a
pale rose colour, more or less transparent, and which lives with its
companion, the pinnothere, in the cavity of the _Pinna marina_. This
is the same animal which a naturalist of the last century named the
_Cancer custos_.
We have wished to ascertain whether Pliny knew these crustaceans. He
has spoken of them in the following terms:--"The Chama is a clumsy
animal without eyes, which opens its valves and attracts other fishes,
which enter without mistrust, and begin to take their pastime in their
new abode. The pinnothere seeing his dwelling invaded by strangers,
pinches his host, who immediately closes his valves, and kills one
after another these presumptuous visitors, that he may eat them at his
leisure."
Cuvier did not believe that the pinnothere brought any food to the 19
mollusc, since the latter, in his opinion, lives entirely on
sea-water.
Other zoologists regard the pinnothere as an intruder whom chance has
brought into this mysterious position. Others again consider mussels
as acquaintances possessed of a very curious disposition, and that
having no eyes, they have interested in their fate this little crab,
which is perfectly provided with eyesight. In fact, in common with
other crustaceans of his species, he carries on each side of his
carapace, at the end of a movable stalk, a charming little globe,
provided with some hundreds of eyes, which he can direct upon his
prey, as the astronomer turns his telescope on any point of the
firmament. These later naturalists consider, in fact, their crab as a
living journal which supplies his host with the news of the day.
Rumphius, a Dutchman, the first who described the animal of the
nautilus, also understood the habits of pinnotheres. In his "Amboinche
Rariteit Kamer," published in 1741, he says that these crustaceans
inhabit always two kinds of shellfish, the _Pinna_ and the _Chama
squamata_. According to him, when these molluscs have attained their
growth, one pinnothere (one only at least in the Chama) lives in their
interior and does not abandon its lodging till the death of its host.
Rumphius regards this crustacean as a faithful guardian, fulfilling
the duties of a door-keeper. In 1638 he found actually two sorts of
keepers: by the side of a Brachyuron, carrying an embossed buckler,
slender in front, he discovered a Macrouron of the length of his
finger-nail, of a yellowish orange colour, semi-transparent, with
white and very slender claws. It is without doubt the same animal 20
that Mons. Peters, of Berlin, found on the coast of Mozambique, and of
which we have spoken before.
A little crab is known to live near the coast of Peru (_Fabia
Chilensis_, Dana), which exists under somewhat different conditions.
He chooses, not a bivalve mollusc, but a sea-urchin (_Euriechinus
imbecillus_, Verrill), and lodges in the intestine, near its
termination, so as to seize as they pass by all those living creatures
which are attracted by the odour. Doubtless, the delicacy of our sense
of smell is disgusted by such a mode of seeking food; but this
predilection may have a reason with which we are not acquainted. There
are a considerable number of other species which live under similar
conditions.
On the coast of Brazil, my son found two couples of crabs in the tube
of a very long annelid, narrow at the ends, and wide in the middle.
The tube was too small at the end to allow them to escape. These
crustaceans had, no doubt, penetrated thither before they had attained
their full size.
A crab of the family of the Maidæ conceals itself in the substance of
a polypidom very common in the Viti Islands, in company with a
gasteropod mollusc, and both of them assume the exact colour of the
polypidom. This is a new kind of _mimicry_. This crab is known by the
name of _Pisa Styx_, the gasteropod is a _Cypræa_, the polyp is the
_Melithea ochracea_. A decapod crustacean, the _Galathea
spinirostris_, seeks for a _Comatula_, the colour of which it exactly
imitates, and with which it lives on the most friendly terms.
The holothuriæ, of which we have already spoken, appear to afford an
abode to many animals: independently of the _Fierasfer_, the 21
_Holothuria scabra_ of the Philippine Islands regularly lodges in
its interior a couple, and sometimes, though rarely, a greater number
of pinnotheres belonging to two distinct species. They choose this
domicile at an early period, and must be highly delighted with this
obscure abode, since they are seen no more, and when they have once
entered never quit this living cavern. This observation is due to
Professor Semper, who has made us acquainted with so many curious
facts of the China Sea and the Pacific Ocean. In the midst of the
slender branches of a coral of the Sandwich Islands, the _Pæcilopora
cæspitosa_ of Dana, there lives a little crab (_Hopalocarcinus
marsupialis_, Stimpson), which is at last completely enclosed by
the vegetation of the coral. It only keeps up sufficient communication
with the exterior to enable it to procure food. The coral, however,
furnishes it nothing but a resting-place in the midst of its tissues.
Among the Philippine Islands, also, a brachyurous crustacean lives in
the branchial cavity of one of the _Haliotidæ_, and another on the
body of a holothuria. On the coasts of Brazil, F. Müller, during his
abode at Desterro, saw some _Porcellanæ_ inhabiting star-fish, not as
parasites, as had been supposed, but as true messmates. A crustacean
possessed of but little generosity is the _Lithoscaptus_ of Mons.
Milne-Edwards. Provided with beak and claws for the purpose of attack,
it instals itself, sad to say, in the pantry of a medusa, and instead
of making use of its own weapons, takes advantage of the perfidious
nematocysts of its acolyte, in order to live quietly at his expense.
Under the name of _Asellus medusæ_, Sir J. G. Dalyell has made 22
us acquainted with another messmate of the medusæ which greatly
resembles an _Idothea_.
Another kind of commensalism is that of the Dromiæ. These crabs are of
the ordinary size, and lodge, from their earliest youth, under a
growing family of polyps, which increases with them. This colony has
for its principal foundation a living Alcyonium, which covers the
carapace, and as it develops, adapts itself perfectly to all the
inequalities of the cephalothorax; one might consider it an integral
part of the crab. Sertulariæ, Corynes, Algæ, develop themselves on
this Alcyonium, and the Dromia, masked by this living rock which it
carries on its shoulders like the fabled Atlas, marches gravely in
pursuit of her prey. She has no fear of arousing the attention of her
enemies. The greatest vigilance cannot prevent the sudden attack of
these dangerous neighbours. There is in the Mediterranean a species
which sometimes comes to our coast. They are also known in the Indian
Seas and in the Northern Pacific. Rumphius named the dromia _Cancer
lanosus_; it is, said he, a crab which carries grass or moss on its
back. It is also mentioned by Renard. Dana has observed a sea-anemone
covering a crab in the same manner as the Alcyonium does the dromia,
and which is not less dangerous. The mode of life of this anemone has
procured for it the name of _Cancrisocia expansa_. In the north
of California, a crab (_Cryptolithoides typicus_) covers itself
in the same manner with a living cloak which hides it from view, and
under cover of which it surprises those whom it attacks. It has
already cleared the ground of its prey before any alarm has been given
to the neighbourhood.
We should perhaps speak here of an association of another kind, the 23
nature of which it is difficult to ascertain; I refer to the little
crab, the Turtle Crab of Brown, which is met with in the open sea on
the carapace of turtles, and sometimes on sea-weeds. It may be
supposed that it takes advantage of the carapace of its neighbour, in
order to transport itself at little expense into different latitudes,
and it is asserted that the sight of this crustacean gave confidence
to Christopher Columbus, eighteen days before the discovery of the New
World. Besides this animal, a whole society chooses this movable
habitation: in addition to the cirrhipedes we also find the
_Tanaïs_, which is not, however, condemned to live there always.
The macrourous decapods are more rarely found as messmates, but still
a Palæmon is sometimes seen on the body of an Actinia, according to
Semper, and another in the branchial cavity of a Pagurus. But that
which is more generally known, is the presence in the _Euplectella
aspergillum_ of the palæmon which lodges in this fairy palace. It is
probable that the Euplectella of the Atlantic, recently observed near
the Cape Verd Islands by the naturalists on board the _Challenger_,
also conceals this crustacean in its interior. We may also allude here
to the _Hypoconcha tabulosa_, a crab whose carapace is too soft to
allow it to venture out undefended, and which covers itself with the
shell of a bivalve mollusc.
Among the various associations of this kind, none is more remarkable
than that of the soldier-crabs, so abundant on our coasts, and called
by the names of _Bernard the Hermit_ and _Kakerlot_ by the Ostend
fishermen. It is well known that these crabs are decapod crustaceans,
very like miniature lobsters, which lodge in deserted shells, and 24
change their dwelling-place as they grow larger. The young ones are
content with very little habitations.
The shells which give them shelter are such as have been shed, which
they find at the bottom of the sea, and in which they conceal their
weakness and their misery. These animals have an abdomen too soft to
bear the dangers which they meet with in their warfare, and that they
may be less exposed to the claws of their numerous enemies, they take
shelter in a shell which serves at the same time both as a dwelling
and a buckler. Armed cap-à-pie, the soldier-crabs march boldly on the
enemy, and know no danger, since they always have a secure retreat.
But this animal does not live alone in this asylum. He is not so much
of an anchorite as he appears to be, for by his side an annelid
usually instals himself as a messmate, which forms with the Pagurus
one of the most terrible associations that are known. This annelid is
a long worm, like all the nereids, whose supple and undulating body is
armed along its sides with arrows, lances, pikes, and poniards, the
wounds of which are always dangerous. It is a living panoply which
glides furtively into the enemy's camp without giving the alarm.
When a pagurus is on the march it resembles a nest of pirates, who
never cease their exploits till all has been ravaged around them. This
shell is so innocent in its appearance, that it introduces itself
everywhere without provoking the least suspicion. It is usually
covered with a colony of Hydractiniæ, and in the interior,
Peltogasters, Lyriopes, and other crustaceans often establish 25
themselves. The paguri are not messmates of an ordinary kind, for they
inhabit only a deserted shell. They are spread over all seas. They are
found in the Mediterranean, the Northern Sea, on the coasts of the
Pacific, of New Zealand, and of the East Indian islands: thirty
species and even more have been inserted in the catalogue of
crustaceans.
Naturalists have given the name of _Cenobitæ_ to some pagurians
inhabiting the seas of warmer latitudes; these have an abdomen like
the pagurus, antennæ like the _Birgus_, and like it they inhabit
shells. The _Cenobita Diogenes_ is a species found in the Antilles.
Other pagurians, the _Birgi_, grow very large, and conceal their
abdomen no longer in a shell, but in the crevices of the rocks, as
lobsters do at the moulting time, to protect their body while deprived
of their defensive armour. In the East Indies they remain on land, and
even climb into trees. They have so much strength in their pincers,
that Rumphius relates of one of these crustaceans, that, while
stretched on a branch of a tree, it raised a goat by the ears.
Side by side with the pagurians which instal themselves in a shell
with thick and completely opaque walls, we recognize crustaceans of
the order of amphipods, the _Phronimæ_, which choose for themselves
not an abandoned hovel, but a veritable crystal palace, and take
possession of it without inquiring whether or no it is inhabited. The
daylight penetrates through the walls of their dwellings, and it can
scarcely be discerned in the water whether or no their body is
protected by a covering. They usually take the dwelling of a Salpa, a
Beroë, or a Pyrosoma, and from within this lodging they give 26
themselves up to the pleasures of fishing.
The _Phronima sedentaria_ which lodges with the salpa seems to be
scattered over the warm seas of both hemispheres. For the honour of
the species, the females alone seek the assistance of their
neighbours, without at the same time abandoning their characteristic
robe. The sexes differ little from each other except in size, in the
abdomen, and in the antennæ. Maury has described certain amphipod
crustaceans which also inhabit the Salpæ.
Another phronima described by Professor Claus, the _Phronima
elongata_, lives in the same manner; but instead of occupying a
living house, it generally seeks an empty lodging, in which it
establishes itself like a pagurus.
The "Bernard the Hermit" of the Marseillaise fishermen, the _Pyades_,
becomes the messmate of an anemone which Dugès has called _Actinia
parasitica_. According to the observations of the learned professor at
Montpelier, the mouth of this anemone is always situated opposite to
that of the crustacean, to take advantage of the morsels which escape
from his pincers. Both of them profit by this association; and the
opening of the shell is prolonged by a horny expansion furnished by
the foot of the actinia.
On the coast of England lives another soldier-crab (_Pagurus
Prideauxii_), which has as its principal messmate a sea anemone
called _Adamsia_, which Mons. Greeff found at the island of
Madeira. This pagurus is especially remarkable for the good
understanding which exists between himself and his acolyte--he is a
model Amphitryon. Lieut.-Col. Stuart Wortley has watched it in its
private life, and thus relates the result of his observations: this 27
animal after he has fished, never fails to offer the best morsels to
his neighbour, and often during the day, ascertains if it is not
hungry. But more especially when he is about to change his dwelling,
does he redouble his care and his attention. He manoeuvres with all
the delicacy of which he is capable, to make the anemone change its
shell; he assists it in detaching itself, and if by chance the new
dwelling is not to its taste, it seeks another until the _Adamsia_ is
perfectly satisfied. This association is not confined to the union of
a decapod with a nereid and an actinia; a curious cirrhipede often
establishes itself on the body of the pagurus, and on the outside of
the shell we generally find a colony of polyps, of a rose or yellow
colour, which extend like a living carpet round this habitation.
Thirty-six years ago we have given the name of _Hydractinia_ to these
polyps, which were till then entirely unknown to naturalists, and
which form habitually a double overcoat for the paguri, if I may
employ the expression of my learned colleague, Mons. Ch. Desmoulins.
In the Mediterranean lives the _Perella di mare_ of the Italian
fishermen, the _Reclus marin_ of the Marseillaise; this Alcyonium
ought, by its manner of life, to be placed near the Hydractiniæ, and
has been carefully studied by Mons. Ch. Desmoulins. It is the
_Alcyonium_ (_Suberites_) _domuncula_ of Lamarck and Lamouroux.
The abdomen of these paguri is not only sheltered in a shell, but
habitually visited by isopod crustaceans, described under the names of
_Athelea_, _Prosthetes_, and _Phryxus_, which have entirely lost the
livery of their order.
In the same association we also find the _Liriope_, a little isopod 28
crustacean, of which much has been said, but which for a long time
obstinately resisted all attempt at observation.
This latter personage is an isopod crustacean, of moderate size, which
chooses the Peltogaster as a place of abode, after having undergone a
very curious regressive metamorphosis. In fact, the young lyriope has
at first its little feet like other isopods, but in the adult state,
the female loses her antennæ, and changes her buccal as well as her
branchial appendages, so as to assume a different appearance. Several
naturalists have already endeavoured to give the life-history of this
singular Bopyrian. The illustrious Rathke of Königsberg discovered it;
Professor Lilljeborg, of the University of Upsal, gave the first
account of it; and finally Professor Steenstrup of Copenhagen made
known its true origin. In short, the Lyriopes are Bopyrian Isopods,
living on cirrhipedes (Sacculinideæ) as real messmates, if not as
parasites; the male preserves his dignity and his prestige, but the
female strips herself of all the attributes of her sex, and descends
to the lowest degree of servitude.
Faujas de Saint-Fond has mentioned a fossil hermit-crab as found in
the mountain, St. Pierre de Maestricht; but he called by this name a
crustacean of the genus _Callianassa_ and not a pagurus. These
_Callianassæ_ are always completely isolated in the chalk, and it is
probable that they have no other domicile than the sand or ooze at the
bottom of the sea, in which they hollow out galleries for themselves.
Lobsters act in the same manner after moulting. The _Gebiæ_ live like
the Callianassæ, hidden in the mud. The _Limnaria lignorum_ and the 29
_Chelura terebrans_ dig out a retreat for themselves in wood, like the
Teredines.
We have just seen that the higher crustaceans, with their well-mounted
eyes, their enormous antennæ, and their formidable pincers, are not
all of them the great lords they pretend to be; more than one of them
has to hold out its hand and to accept humbly the assistance of its
neighbours.
In the group of isopod crustaceans we find many necessitous beings,
which, too proud to ask for food, are contented to take their place on
some fish which is a good swimmer, which they abandon as soon as their
interest demands it; if their host conducts them to regions that do
not suit them, or if they have otherwise to complain of him, they give
him up, and begin their maritime peregrinations with a fresh
colleague. They always preserve all their fishing tackle and their
sailing gear, and the female does not change her dress any more than
the male. We have to notice that these crustaceans often identify
themselves so entirely with their host that they seem to be a portion
of him, and even to assume his peculiar colour. This is not a sign of
servility, but a means of passing unobserved, and of escaping from the
sight of the enemy that is watching them. Naturalists have given the
name of _Anilocræ_ to some of these free messmates.
Any one who has remained for some time on the coast of Brittany,
especially at Concarneau, and who does not look with indifference on
the many superb fishes which are taken every day, cannot fail to have
been struck with the presence of a rather large crustacean,
which clings to the sides of several kinds of _Labra_, especially 30
the smaller species. This crustacean is an Anilocrian so common that
we can scarcely imagine it to have escaped the attention of any
naturalist. Nevertheless, no work makes mention of the regular
attendance on the Labra by the Anilocra, which bears, we know not why,
the specific name of _Mediterranean_. Rondelet was probably acquainted
with it, when he spoke of the fish-lice, which do not derive their
birth from these fishes, but from the sea mud. We often see males by
the side of females on the same individual.
Some years ago a school of large cetaceans, known under the name of
Grindewhalls or Globicephalæ were pursued in the Mediterranean, and
those which were captured contained in the cavity of their nostrils,
isopods closely allied to the _Cirolana spinipes_, if not identical
with it. Till then the isopods had only been found on sea fishes;
fresh-water fish are not, however, entirely exempt; in fact, a species
of OEga (_OEga interrupta_ of Martens) has just been found on the skin
of a fresh-water fish of Borneo, the _Notopterus hypselonotus_. This
same genus includes a species (_OEga spongiophila_) which lives in the
magnificent sponge, the _Euplectella_. We know also a certain number
of isopods which prefer the interior of their neighbour's body, and
instal themselves in the cavity of the mouth, either to fish at the
same time as their host, or to seize the food on its passage; others
are of such a cruel nature, that they make no scruple to establish
themselves in the stomach of a peaceable white fish. Without injuring
any important organ, they penetrate in couples between the intestines,
and, concealed in this retreat, they seize by the narrow entrance door, 31
which they keep half open, all the little animals which are
sufficiently bold to pass by. The cruelty of these beings knows no
bounds. To instal themselves conveniently, they pierce the body of
their host, skilfully open his stomach, and live there as Sybarites;
their lodging is in future assured to them, and their fate is bound up
with that of their host. Dr. Herklots, who has unfortunately been
recently lost to science, communicated in 1869, to the Academy of the
Netherlands, a very interesting memoir on two crustaceans of a new
species, the _Epichtys giganteus_, which lives on a fish of the Indian
Archipelago, and the _Ichthyoxenus Jellinghausii_, which lodges in a
fresh-water fish of the Island of Java. It is to the latter that we
refer here, and it seems that in this species we are approaching the
limits at which commensalism commences.
The _Cymothoes_ constitute another category of very interesting
Isopods; they lodge with their female in the cavity of a fish's mouth.
Dr. Bleeker, who has so successfully explored the Indian seas,
obtained more than twenty species of these; but unfortunately he has
not made a note of the fishes which harbour them. He has, however,
made one exception with regard to a fish from the roadstead of
Pondicherry, which is two feet long, and is called a Bat. It is known
to naturalists under the name of _Stromatea Nigra_; its flesh is much
esteemed, and it carried in its mouth a Cymothoe called by Dr. Bleeker
_Cymothoe Stromatei_. A cymothoe has also been observed in the mouth
of an Indian Chetodon. De Kay found one in a Rhombus in the United
States, and De Saussure saw another at Cuba; and lately, Mons. Lafont
discovered one in the Bay of Arcachon, on the _Boops_, and on the 32
_Trachina vipera_. These cymothoes are about fifteen millimetres in
length, and often fill all the cavity of the mouth. The most curious
of all is that which is found in the mouth of the flying-fish, a kind
of herring with elongated fins, which it uses as wings to rise into
the air, when too closely pursued in the water. My son, when examining
these fishes, in his passage from Cape Verd to Rio de Janeiro, found
in the cavity of their mouth an enormous female, firmly wedged in the
branchial arches, with its head inclined outwards, and the male, which
was rather smaller, installed at her side. Their dwelling thus by
pairs, as well as the entire conformation of the animal, plainly shows
that these crustaceans make themselves at home, and live as true
messmates. Cunningham has given them the name of _Ceratothoa exoceti_.
A short time since, these Cymothoes were only known on marine fishes,
but it appears from recent observations, that fresh-water fish are far
from being exempt from them. Mons. Gertsfeld has recently noticed some
on the _Cyprinus lacustris_ of the river Amour, and another in the Rio
Cadea in Brazil, on a _Chromida_. Other isopods also resort to fishes,
and to animals of their own class, but they live as true parasites,
and change their form as soon as they have chosen a resting-place. We
shall return to this subject again. Some which are very common on
prawns, are known under the name of Bopyrus.
An interesting division of amphipods have received the name of
_Hyperinæ_. These crustaceans generally swim with facility, but walk
with difficulty. They therefore usually have recourse to fishes, or
even to medusæ, in order to gain support. We find on our own coasts
the _Hyperina Latreillii_, lodged in the superb _Rhizostoma_, which 33
regularly appears in the later season of the year on the coast of
Ostend; and a long time since, in 1776, O. F. Müller gave to a species
of this genus the name of _Hyperina medusarum_. Mr. Alexander Agassiz
once found a _Hyperina_ on the disc of an _Aurelia_. The medusa, when
extended, forms for them a balloon with its parachute, which supports
and conveys them with greater or less rapidity. Professor Möbius has
but lately remarked the presence of _Hyperina galba_, Mont., in the
_Stomobrachium octocostatum_, Sars, a small species of medusa which
appears in the Bay of Kiel in October and November. This naturalist
supposes that these messmates at first inhabited the _Medusa aurita_,
and then migrated into this species.
Besides these, there are _Gammari_, which, according to Semper, live
in the _Avicula meleagrina_ (pearl mussel), and are perhaps the
principal manufacturers of fine pearls. The immense buccal cavity of
the fishing-frog (_Lophius piscatorius_) is the abode in the
Mediterranean of an _Apterychta_, and in the Northern Ocean of a
curious amphipod of the ordinary size of the _Gammarus_, which takes a
voyage without expense, and with no fear of wanting provisions. My son
discovered it at Ostend, and proposes the name of _Lophiocola_ to
distinguish it. The Gammari give lodging themselves to a great
quantity of parasites, which they must introduce into the bodies of
those to whom they serve as food. It has been long known that whales
have lice, to which naturalists have given the name of Cyami. They are
found on the whales of both hemispheres, and on some other cetaceans.
It is very remarkable that they are seen on the true whales of 34
the north and of the temperate regions, on the _Megaptera_, and on
several _Catodonta_, and that none are found in the _Balenoptera_. Mr.
Dall has just noticed some on the singular _Grey Whale_ of California.
In general, we may say that each cetacean which harbours them, has its
own species. Are they parasites or messmates? If we are to believe
Roussel de Vauzème, they feed on the skin itself of the whale, the
remains of which, it is said, are found in their stomach. According to
this naturalist, the parts of the mouth are not adapted for suction,
and the stomach contains ruminating apparatus. We think that a fresh
examination is necessary before this question can be determined. The
_Cyami_ seem to us to live on the whale, as the _Arguli_ and the
_Caligi_ do on fish; and if these living creatures derive their
nourishment only from the mucous products secreted by the skin, we may
ask whether they ought not to be classed in a separate category, for
they ought not to figure on the list of paupers. We have found the
orifice of the _Tubicinella_ covered with cyami of every age, and
their abundance in this place seems to indicate that their food was
not supplied to them by the skin of their host. Mons. Ch. Lutken has
recently published a very interesting monograph on these curious
animals; according to him the _Cyamus rhytinæ_, which was thought to
proceed from a piece of the skin of a _Stellerus_, appears to have
been found on the skin of a whale.
The Picnogonons, the nature as well as the kind of life of which has
been so long time problematical, deserve to be ranked among messmates,
at least during their youth; in fact, after being hatched, they live on
the _Corynes_, the _Hydractiniæ_, and other polyps, while at a later 35
period they frequent molluscs or higher classes; Allman mentions the
case of a _Phoxichilidium coccineum_ lodged in a _Syncoryne_.
There are, perhaps, many other crustaceans which, placed among
messmates, like the _Pandarus_ and others, would have a right to
claim a further inquiry. It is a fact that they are never seen except
on the skin of their host, where they are always visible, preserve
their colours entire, and never change their costume for the undress
of a parasite. The _Pandari_ live especially on the _Squalidæ_. Some
which are found in our seas are of rare elegance of form. We must,
perhaps, place among messmates the crustacean which Siebold found in
the Adriatic, at Pola, on the belly of the worm _Sabella ventilabrum_,
and it is not impossible that the _Staurosoma_ observed by Will on an
actinia, should have its place here rather than among the parasites.
A Rotifer without vibratory ciliæ, the _Balatro calvus_ of Claparède,
lives as an epizoon on the same annelids which lodge the Albertia in
their interior. The Darwinists, observes Claparède, will not fail to
remark the presence of these Rotifers of the genus Albertia in the
interior of the animal, and of the genus Balatro on the exterior. The
parasite Balatro, like a shadow, never quits his Mecænas, says the
learned naturalist of Geneva; who has observed it on the _limicolous
Oligochæts_ of the Seime, in the Canton of Geneva.
The _Nebalia_ of Geoffroy is an interesting crustacean, abundant on
the coast of Brittany. This charming animal gives lodging habitually
to a messmate which Mons. Hesse considered as an animal allied to the 36
_Histriobdellæ_, but which is only an imperfectly described Rotator.
We believe that it is the same animal to which Professor Grube has
given the name of _Seison nebalia_. It appears to assume the aspect of
the Histriobdellæ, and may perhaps be adduced as an example of
mimicry.
The molluscs, whatever their name may imply, are those which show the
most independence among all the inferior ranks of animals; not only
are they contented with the slowness of their pace and the
wretchedness of their food, but they only very rarely seek help from
their neighbours. It is not, however, uncommon to find some living
among corals, which have even been designated coralligenous molluscs.
There exists a group of Gasteropods, the Eulimæ, which lodge in
certain Echinoderms, and in every respect deserve to be classed among
messmates; it was a long time before the relation which exists between
them and the animals which shelter them had been thoroughly
appreciated. Dr. Gräffe found one species, the _Eulima brevicula_, on
the _Archaster typicus_ of the Uvea Islands, in the Pacific Ocean. The
molluscs, known by the name of _Stylifer_, have the same mode of life;
they have been observed in the Asteriæ, the Ophiuræ, the Comatulæ, and
even in the Holothuriæ; and as they inhabit the digestive cavity of
these animals, it was believed that they frequented them as parasites.
This was the opinion expressed first by d'Orbigny, and adopted by most
naturalists. Professor Semper found some in the skin of a holothurian
(_Stichopus variegatus_), which he considered incapable of nourishing
themselves otherwise than at the expense of their host. However this
may be, these molluscs, ranged alternately among the _Phasianellæ_,
the _Turritellæ_, the _Cerithia_, the _Pyramidellæ_, the _Scalariæ_, 37
the _Rissoairia_, or in a distinct family, seem to belong rather to
messmates than to parasites. We meet with Stylifers at the entrance of
the mouth (Montacuta); more frequently they prefer, like the
Fierasfers, to lodge themselves deeply in the digestive cavity in the
midst of the _débris_ of the prey. The Melania (_M. Cambessedesii_,
Risso), which Delle Chiaie found in the Bay of Naples, on the foot of
some comatulæ, belongs probably to this group of molluscs.
Among the gasteropod molluscs which are not able to maintain
themselves, we may mention another, a curious parasite, which instals
itself in one of the rays of a star-fish, and whose presence is
revealed by a swelling which is not produced in the other rays. This
mollusc has received the name of _Stylina_.
The molluscs which are the most remarkable from the point of view from
which we are now considering them, are the _Entoconchæ_; they live in
Enchinoderms, and it was thought for a while that we could see in them
an example of the transformation of one class into another. Some years
since J. Müller found in a Synapta from the Adriatic, tubes with male
and female organs, without any other apparatus, and in these tubes
appeared eggs, whence this great physiologist saw molluscs proceed,
with a helicoid shell, similar to that of a small natica; he gave them
the name of _Entoconcha mirabilis_. Professor Semper has since
discovered another species of these, which he has dedicated to the
illustrious physiologist of Berlin, and which he found attached to the
cloacal sac of the _Holothuria edulis_.
The true relation between these molluscs and the holothurians remains 38
to be discovered, and how the entoconchæ become at last simple sexual
tubes. At present we must admit that it is the result of a
retrogressive development like that of the peltogasters, which, like
them, lose all the attributes of their class. They ought, perhaps, to
be placed farther on, among parasites.
Some years since, some molluscs were observed which have compromised
more or less the dignity of their class. Gräffe cites a species of the
genus _Cypræa_, which one would certainly not expect to find in this
category; it lives among the Viti Islands, in the compartments of the
_Milithæa ochracea_. We have referred to it before. Naturalists have
given the name of Melithæa to a very beautiful polyp which forms
colonies of two or three metres in height. Mons. Steenstrup, with that
perspicacity which discerns the most complex phenomena, has also
described _Purpuræ_ which live as messmates with the Antipathes and
the Madrepores. Quite recently, indeed, Mr. Stimpson has observed in
the port of Charleston, a gasteropod mollusc, similar to a Planorbis
(_Cochlioelepsis parasitus_) which lives as a messmate in the body of
an annelid (_Ocoetes lupina_).
It is not the same with a mollusc called _Magilus_, which naturalists
considered for a long time to be the calcareous tube of an annelid.
All conchologists know the shell of the Magili, so valued by
collectors. This gasteropod when young takes up its lodgings in the
substance of a madrepore which grows more quickly than he, and in
order not to die, stifled in this living wall, he constructs a
calcareous tube similar to the shell, of which it appears to be the
continuation, and which allows it to procure for itself water, air, 39
and food. The animal, protected by the madrepore, can do without its
calcareous mantle, and only shows the end of the tube at the outside.
It is this organ which sustains the struggle against the exuberant
growth of the polyp, since it is by means of it that the mollusc
obtains nourishment. The Magilus is like an oyster which is living in
contact with a bank of mussels, with this difference, that the oyster
almost always succumbs, while the magilus is always victorious in the
struggle. We might also cite as well as the Magili, some _Vermeti_,
certain _Crepidulæ_ and _Hipponices_, which struggle with the same
success against those which pilot or receive them.
As there exist parasites which only depend on others during their
youth, so there are messmates which are completely independent when
fully grown. Jacobson, of Copenhagen, wrote, in or about 1830, a
memoir to show that the young bivalves which are found in the external
branchial processes of the Anadontæ are parasites, and he proposed for
them the name of _Glochidium_. Blainville and Duméril were charged to
make a report on this memoir, which the author had sent to the
Académie des Sciences. But his opinion had not many supporters, and it
is now thoroughly known that the young anodonts differ considerably in
their early and their full-grown state. During their stay in the
branchial tubes, each young animal carries a long cable which descends
from the middle of the foot, and serves to attach the anodont to the
body of a fish, and yet permits it to move to a certain distance.[1]
In fact the young anodonts have, not like the other acephala, 40
vibratory wheels in order to move themselves; they are conveyed in
this manner by their neighbours. There are also messmate acephala, as
the _Modiolaria marmorata_, which lodge on the mantle of ascidians.
Professor Semper found attached to the skin of a _Synapta similis_, a
mollusc which possesses a peculiarity rare among these animals, that
of carrying its shell in the interior and not on the outside.
There are few animals so infested with parasites as the Ascidians in
general. Not only does their surface sometimes become a _microcosm_,
as the name of one Mediterranean species indicates, but even in the
substance of their testa lodge _Crenellæ_ and other molluscs and
polyps, which choose by preference to place their dwelling there.
There are also Annelids which hollow out galleries in their interior,
Lernæans which establish themselves in their respiratory cavity,
Nematodes, Pycnogonidæ, Ophiuræ, and many others besides. Mons. Alfred
Giard has described several Amphipods and Isopods which establish
themselves on Tunicates. One cannot say that there is always such a
complete agreement between animals of such different kinds, for Mons.
Alfred Giard gives examples of grave disagreements which he has seen
break out, and which have caused the death of several among them.
Another association is that of a gasteropod with one of the acephala.
In the environs of Caracas lives an Ampullaria (_Crocostoma_) which
lodges in the umbilicus of its shell another mollusc, the only
fluviatile species of those countries, called the _Sphaerium
modioliforme_. We have every reason to suppose that the Sphaerium
lives on good terms with the Ampullaria, since they are usually found
associated.
The Bryozoaria, the animal mosses, establish themselves on all solid 41
bodies at the bottom of the sea, like true mosses on stones or on
trees. One species, a _Membranipora_, is usually found on the common
mussel. These animals are of small size, group themselves in colonies
on the surface of shells and of polyparies, or even on crustaceans,
and form by their union a fine kind of lace, the dazzling whiteness of
which often comes out sharply on the varying and glittering colour of
the shell. This is because each animal lodges in a cell which is not
larger than the head of a pin, and all the cells of a colony are
grouped together with the symmetrical regularity of the façade of a
Gothic building.
Many Bryozoaria live in such a manner that it is impossible to say
whether they are messmates, or have installed themselves by chance in
a hiding-place for which they have no predilection. A charming
bryozoon is developed in abundance on the carapace and the claws of
the _Arcturus Baffini_, on the coast of Greenland, and propagates
itself with extreme rapidity. On a single Arcturus we have found,
scattered over its claws by the side of each other, Balani, Spirorbes,
Sertulariæ, and vast colonies of Membranipora. One can see, merely by
this example, the great zoological riches of the polar seas.
Certain annelids off the coasts of Normandy and Bretagne are the
abodes of a bryozoary known under the name of _Pedicellina_, or
_Loxosoma_. This interesting animal, which my fellow-labourer, Mons.
Hesse, took for a Trematode, and whose drawings had led me into error,
lives like others at liberty while young, and soon fixes itself to a
Clymenian, in order to pass as a messmate the later period of its
life. We have called it _Cyclatella annelidicola_, because of 42
its residence in a Clymenian annelid. Claparède and Keferstein have
observed a species, the _Loxosoma singulare_, on a capitellian
annelid, of the genus _Notomastus_, at St. Vaast-la-Hogue, on the
coast of Normandy. After this, Claparède found another species, the
_Loxosoma Kefersteinii_, in the bay of Naples, on an _Acamarchis_, a
bryozoarian mollusc. Mons. Kowalewsky has observed in the Bay of
Naples the _Loxosoma Napolitanum_.
We found some years ago the Pedicellinæ in so great abundance in the
oyster beds of Ostend, that the baskets and other things floating on
the water were literally covered with them. We have several times
since endeavoured to procure them again, but it was in vain to search
in the same places where they were formerly so abundant: we have not
been able to discover a single one.
The class of worms includes not only parasites, it contains also, as
we shall see, true messmates; we find some on crustaceans, on
molluscs, on animals of their own class, on Echinoderms, and on Polyps.
One of the most curious of these worms is the _Myzostoma_, whose true
nature has just been revealed by the excellent researches of Mons.
Mecznikow. These myzostomes resemble trematode worms, but they have
symmetrical appendages, and are covered with vibratory ciliæ. They
live on the comatulæ, and run upon these echinoderms with remarkable
rapidity. They have not hitherto been found elsewhere; they are
evidently no more parasites than the last mentioned, and their place
is among free messmates. Two great annelids are found, the one, the
_Nereis bilineata_, by the side of Paguri in the same shell, the other,
the _Nereis succinea_, according to Grube, in the tubes or galleries 43
of the Teredines. These dangerous acolytes introduce themselves
furtively into the retreat of their host; and, always on the watch,
they obtain at all times, and in every place, a certain prey, and a
hiding-place from which they can take their share of their neighbour's
goods. Another nereis, observed by Delle Chiaie, _Nereis tethycola_,
lives in the cavities of a sponge, the _Tethya pyrifera_, which is
visited by so many messmates and parasites, that it becomes a kind of
hotel, where every one establishes himself at his ease. Risso also
mentions a _Lysidice erythrocephala_ which lives in sponges.
In the same class is found an Amphinoma, a beautiful red-blooded worm,
which proudly wears a plume of red branchiæ on its head, and which
Fritz Müller observed on the coast of Brazil, begging assistance from
a poor _Lepas anatifera_. Many Polynoës live upon other annelids; the
_Harmothoë Malmgreni_ on the sheath of the _Choetopterus insignis_,
the _Antinoe nobilis_ on the case of the _Terebella nebulosa_. Prof.
Ray Lankester has lately communicated some observations on this
subject to the Linnæan Society of London, and Dr. M'Intosh mentions
some new species leading the same kind of life on the coast of
Scotland.
Grube found at Trieste, in a star-fish (_Astropecten aurantiacus_),
between its rows of suckers, a _Polynoë malleata_, with its stomach
attached to the animal; and Delle Chiaie has lately observed on an
asteria, a _Nereis squamosa_ by the side of a _Nereis flexuosa_. Mons.
Grube thinks that the nereis of Delle Chiaie is no other than the
_Polynoë malleata_. Lobsters are often covered with very small
tubicular worms, which invade the whole carapace, and which, as true 44
messmates, give themselves up to the caprices of their host. These are
a kind of _Spirorbis_, which, under the form of small spiral tubes,
instal themselves, by preference, on the limbs, the antennæ, or the
claws.
Mr. A. Agassiz has seen on the coast of the United States, a Beroë
(_Mnemiopsis Leidyi_) which gives lodging in its interior to worms
which somewhat resemble the Hirudinidæ, and which doubtless live there
as messmates. Mr. A. Agassiz has remarked to me another example of
commensalism. On the coast of the territory of Washington, as far as
California, is found a worm of the genus _Lepidonotus_, which always
lives near the mouth of a star-fish, the _Asteracanthion ochraceus_ of
Brandt; sometimes as many as five are found together on a single
individual, and are placed on different parts of the ambulacral rays.
Mr. Pourtalis and Mr. Verril have observed annelids lodged in the
polypidoms of the Stylaster.
There are few fish on which are not found _Caligi_, charming
crustaceans which please the eye by their attenuated shape and their
graceful movements. On these Caligi, which sometimes literally cover
the skin of cod-fish coming from the north, we often find a curious
trematode, the _Udonella_, which resembles one of the small
hirudinidæ. Should this worm be placed among messmates? What is the
part which it plays? We are persuaded that it is the same as that of
the histriobdellæ under the tail of lobsters, that is to say, that it
clears off the eggs of caligi which do not arrive at perfection, but
perish in the course of their evolution.
Roussel de Vauzème has mentioned another worm, a nematode, to which 45
he has given the name of _Odontobius_, and which lives on the palatal
membranes (the whalebones) of the southern whale. It is evidently a
messmate. It can get nothing from the whalebones, but it snaps up on
their passage in the interstices of the baleen, small animals of all
kinds which swarm in these waters. When we open the _Pylidium girans_,
we often find in the interior of its digestive cavity a larva, which
was once thought to be descended from it, but instead of being allied
to the Pylidium, this larva comes from a nemertian known by the name
of _Alardus caudatus_. The young nemertian never abandons his host
until it approaches the period of puberty, and then all the
individuals living under the same conditions emancipate themselves at
once, to pass the rest of their days free and roving like their
mother.
Worms which have less freedom, like the Distomians, are sometimes both
messmates and parasites. We find a remarkable example of this in the
_Distomum ocreatum_ of the Baltic. According to the observations of
Willemoes-Suhm, this trematode passes its cercarial life freely in the
sea, and instead of encysting itself in the body of a neighbour, it
attaches itself to a copepod crustacean, the whole of the inside of
which it devours, in order to clothe itself afterwards with the
carapace of its victim. It is under the cover of its prey that it
passes into the herring, and completes its sexual evolution.
Mons. Ulianin has recently found another Distome (_Distomum
ventricosum_) which passes its cercarial life in freedom in the bay of
Sebastopol, and completes its evolution in the fishes of the Black
Sea. J. Müller has long since found Cercaria living freely in the
Mediterranean.
We ourselves, some years ago, while making some researches among the 46
Turbellaria, found among the eggs of some ordinary crabs of our coasts
(_Carcinus mænas_), an interesting worm which we named _Polia
involuta_, but which Prof. Kolliker appears to have known before, and
designated by the name of _Nemertes carcinophilus_. It is not known
whether it plays the same part as the Histriobdellæ and the Udonellæ.
Delle Chiaie, as well as Prof. Frey and Prof. Leuckart, make mention
of another nemertian which inhabits the _Ascidia mamillata_. Among the
nemertians, we may allude to the _Anoplodium parasita_, which lives in
the _Holothuria tubulosa_, and the _Anoplodium Schneiderii_,
inhabiting the intestines of the _Stichopus variegatus_.
According to Mr. A. Agassiz, a species of Planarian (_Planaria
angulata_, Mull.), lives as a free messmate on the lower surface of
the Limulus, and prefers to establish itself near the base of the
tail. Mons. Max Schultze recognized last year this same messmate on a
limulus, which had died at Cologne in the large aquarium, and which
had been sent to him for his anatomical studies. He showed at the
congress of German naturalists at Wiesbaden, in 1873, the drawing
which he had made of this animal, which he thought new to science. We
may remark in passing, that he arrived, by means of his anatomical
observations on Limuli, at the same result as did my son by his
embryogenic observations, namely, that these supposed crustaceans are
to be regarded as aquatic scorpions. Mr. Leidy also makes mention of
Planarian parasites (_Bdellura_), with a sucker at the extremity of
the body; and Mons. Giard noticed a blue one on the body of a
Botryllus.
But of all the Turbellaria, the genus which appears to us the most 47
interesting is the Temnophila, which Gay first observed on crabs at
Chili, and which Professor Semper afterwards found on the crabs of the
Philippine Islands. Gay and Phillipi found colonies of these animals
on the body, the claws, and more especially the abdomen, of the
_OEglea_. This messmate resembles a trematode by its form and by its
posterior sucker, but by its entire character, and especially by its
sexual organs, it belongs to the _Turbellariæ_. Mons. Blanchard calls
it _Temnophila Chilensis_. Professor Semper saw at the Philippine
Islands these Temnophilæ on river crabs, at five thousand feet above
the level of the sea.
The _Cydippe densa_, a charming polyp of the Gulf of Naples, lodges in
its gastro-vascular apparatus larvæ of annelids, which may as well be
considered parasites as messmates. We owe to Panceri the first
observations on these worms, of which two genera, _Alciopina_ and
_Rhynconerulla_, seem to live in the same manner in their youth. A
naturalist, whose loss is profoundly deplored by the scientific world,
Claparède, occupied himself with observations on these annelids during
the last years of his life. It appears that these worms are so common
in these polyps, that four have been found at once in the same animal.
The Spoon-worm, named by OErsted, _Sipunculus concharum_, ought
doubtless to find its place here. An oligochete worm, _Hemidasys
agaso_, from the Gulf of Naples, lives on the _Nereilepas caudata_,
and Claparède did not think it unworthy of his attention. The surest
means of finding it, says this philosopher, is to look for it on this
annelid; and our much regretted fellow-labourer at Geneva did not 48
abandon this messmate before he had completely studied it. Let
us remark in passing, that Professor Grube published in 1831, at
Königsberg, a special work on the abodes of annelids in general.
Cases of commensalism among the Echinodermata are still more rare.
These animals are sufficiently provided with organs, both with respect
to their food and their skin, not to require the assistance of their
neighbours. We cannot rank as a phenomenon of commensalism, the
conduct of the young Comatulæ, which fasten themselves, as Mr. A.
Agassiz informs me, to the basal cirrhi of the adult echinoderms, and
there form a little colony of young Pentacrinites.
We only know one Ophiurus (_Ophiocnemis obscura_), which lives as a
messmate on a comatula, and consequently seeks assistance from an
animal of its own rank. Another kind of Ophiuride (_Asteromorpha
lævis_, Lym.) fixes itself on a _Gorgonella Guadelupensis_ of
Barbadoes. Everything induces us to suppose that we shall find more
than one species of echinoderm, which will take its place among these
when their mode of life has been studied with greater care. Professor
Lütken has just proved this by quite recently making known another
_Ophiothela_, which lives in the straits of Formosa, and seems to be
the messmate of an Isidian polyp, known under the name of _Parisis
loxa_. Another species (_Oph. mirabilis_) from Panama, infests certain
Gorgoniæ and sponges; a third is found in the Fiji Islands on the
_Melitodes virgata_; a fourth at the Isle of France on Gorgoniæ; and a
fifth at Japan on the _Mopsella Japonica_. There is also another in
the Pacific Ocean, but its companion is not known.
Professor Mobius, as well as Dr. F. Martens, has noticed a _Hemicuryale 49
pustulata_ on a polyp of Jamaica, known under the name of _Verrucella
Guadelupensis_. This is a curious instance of mimicry.
The class of polyps includes several species which seek for assistance
from others, and are classed among messmates. One of the most
remarkable is the Gigantic Medusa, which can extend its arms downwards
to a hundred and twenty feet, and bears the name of _Cyanea arctica_;
the disc is seven feet and a half in diameter, and when the animal is
on the surface of the water, the fringes, which surround the cavity at
its mouth, occasionally afford lodging in the midst of them to a
species of actinia, which lives there as messmate. Sometimes three,
and even four or five, are found on a single Cyanæa. This also is an
observation due to Mr. A. Agassiz, which he has published in his
interesting work, "Sea-side Studies." Prof. Haeckel supposed that the
_Geryoniæ_ produce _OEginidæ_ by means of buds; but it appears that
the learned professor was mistaken as to the nature of these buds;
that instead of being produced one from the other, they have,
according to Steenstrup, a completely different genealogy, being only
united by conditions of good-fellowship. They may be truly called
messmates.
Mons. Lacaze-Duthiers, who went to the coast of Africa to study
corals, met with a young polyp which requires the assistance of
another polyp in its early condition. This animal, to which he has
given the name of _Gerardia Lamarckii_, lives on one of the Gorgoniæ,
which it invades and stifles, as the lianas strangle the tree over
which they spread themselves. But these same Gerardiæ can also
develop themselves on the eggs of the _Plagiostoma_, and are then 50
capable of living separately. In the substance of this polyp lives a
crustacean, the nature of which Mons. Lacaze-Duthiers has not yet made
known.
The superb sponge, _Euplectella aspergillum_, the elegant structure of
which cannot be sufficiently admired, is, unlike the Alcyonium of the
Dromia, rooted to the soil, but nevertheless gives shelter to three
kinds of crustaceans: Pinnotheres, Palemonidæ, and Isopods. These
supposed plants have been known for many years under the Spanish name
of _Regadera_, or the English "Venus' Flower-basket;" they were first
brought from Japan, and afterwards from the Moluccas, and more
recently from the Philippine Islands. In almost all the individuals
which Professor Semper was able to study in those parts, were found
the same crustaceans. These _Euplectellæ_ have just been met with to
the south-west of Cape St. Vincent, by Wyville Thomson, who has
brought up some from a depth of 1090 fathoms, while on board the
_Challenger_. This skilful professor has discovered another sponge to
the north-west of Scotland, at a depth of 460 fathoms; it bears the
name of _Holtenia Carpenteri_; and I have in my possession a fine
specimen which I owe to his generosity, and keep as a _souvenir_ of
the delightful hospitality which he extended to me at the Edinburgh
meeting.
There are also sponges which construct a dwelling in the abode of
their neighbour. We find, among others, a small sponge known under the
name of _Clione_, which establishes itself in the substance of the
shell of oysters, and hollows out galleries as the teredo does in
wood. Mr. Albany Hancock found twelve species of Clione on a single 51
Tridacna. They are evidently not parasites, and I am not sure if their
place is properly among messmates. The oyster, and more especially the
_Ostrea hippopus_, lodges three or four different sorts in its
shell. These Cliones possess siliceous spicules, by means of which
they hollow out galleries in the substance of shells. Mr. Hancock has
published a monograph of this genus, in which he recognizes
twenty-four species collected from different shells, and two other
species, which he refers to the genus _Thoasa_.
The cliones are real lodgers which lead us to the _Saxicavæ_, the
_Pholades_, and the _Teredines_; they seek their lodging in rocks or
in wood; these lead directly to the sea-urchins, which also hollow out
lodgings in rocks, but without penetrating deeply. Professor Allman
has just observed a very remarkable case of commensalism between a
sponge and one of the tubulariæ. The crown of the tubularia is
extended at the entrance of the canals of the sponge; and the
association is so complete, that the Edinburgh professor imagined that
he had before his eyes a true sponge with the arms of a tubularia.
In the lowest ranks of the animal scale, there are certain kinds of
animalcules, which establish themselves on the bodies of obliging
neighbours, and take advantage of their fins in order to swim at their
expense. Thus we often find the bodies of certain crustaceans covered
with a forest of vorticellæ and other infusoria. They cause themselves
to be towed like cirrhipedes, but they do not change their toilet like
them, so that it cannot be said that they put on the livery of
servitude. The kind of life led by several of these animalculæ is as 52
yet little known.
Mons. Leydig has found in the stomach of the _Hydatina Senta_ a
messmate which much resembles an Euglena, and still more the _Distigma
tenax_, Ehr.
[1] I owe this observation to Dr. W. S. Kent, who showed me, in
London, anodonts attached in this manner to sticklebacks.
CHAPTER III. 53
FIXED MESSMATES.
The animals of which we have just spoken usually preserve their full
and entire independence; from the time of their leaving the egg, till
their complete development, they are subject to no other outward
changes than such as belong to their class. If they sometimes renounce
their liberty, it is only for a limited time; and they all preserve
not only their peculiar appearance, but their organs intended for
fishing or for locomotion. It is not thus with those which we are now
about to consider; they are free in their youth, but as they draw near
to puberty they make choice of a host, instal themselves within him,
and completely lose their former appearance: not only do they throw
aside their oars and their pincers, but they cease sometimes to keep
up any communication with the outer world, and even give up the most
precious organs of animal life, not even excepting those of the
senses; they are installed for life, and their fate is bound up with
the host which gives them shelter. The number of these messmates is
considerable.
We shall first allude to some crustaceans named Cirrhipedes by
Lamarck. The metamorphoses which they have undergone since they left
the egg have so much changed them, that Cuvier and all the 54
zoologists of his age placed them in the class of mollusca. The
incrustations of their skin resembled shells, which these creatures
generally carry in the substance of their mantle.
These ambiguous creatures are far from being microscopic; there are
Balani which attain the size of a walnut, and some have been found not
less than ten inches high, as the _Balanus psittacus_. Some years
since we saw on a piece of floating wood, found by fishermen in the
North Sea, Anatifæ on the end of stalks from six to seven feet in
length. The anatifæ themselves were of the usual size. These
cirrhipedes belonged to every geological period; they have already
been found in the Silurian formation, but, unlike the trilobites their
contemporaries, they pass through all the ages, and, far from
decreasing, they reign as masters at the present time in the two
hemispheres.
It was an English naturalist, Thomson, who first made known the true
nature of these singular organisms. So far were many from
understanding their affinities with the other classes, that even after
the excellent researches of the Belfast naturalist, they doubted their
correctness, and supposed that these animals were allied both to the
mollusca and to the articulata.
We see by this the immense progress which embryological studies have
caused us to make in the appreciation of natural affinities. No one at
the present time, who has seen a cirrhipede hatched, can retain any
doubt as to the place which it ought to occupy. These crustaceans,
taken as a whole, lead a life in which we find more than one 55
contrast; all live as wanderers when they first leave the egg, and
they are hatched in such abundance on the coast, that the water
becomes literally troubled with them. At the first period of their
life, they have a supple and elegant body, and fins admirably divided,
and the gracefulness of the postures which they assume does not yield
in beauty to those of the most brilliant insect. After having spent
some time in seeking adventures, they are seized with disgust for a
nomad life; they choose a resting-place, and establish themselves by
means of a cable which they afterwards abandon, and shelter themselves
in an enclosed retreat for the rest of their days. Many cirrhipedes
choose the back of a whale or the fin of a shark, and make the passage
across the Atlantic or the Pacific in less time than the swiftest
steamboats.
In many of these, recurrent development (I was about to say
degradation) sometimes proceeds so far, that their animal nature
becomes doubtful, and more than one of them, having no longer any
mouth by which to feed, are reduced to a mere case which shelters
their progeny. The messmate very nearly takes its rank among
parasites. There are also cirrhipedes which live on different genera
of their own family; and some species which are always found in
society with other species. Some also live as messmates with each
other; some of the Sabelliphili have one of the sexes parasitical on
the other sex.
Crustaceans are usually dioecious; but because of their manner of
life, the cirrhipedes sometimes unite the two sexes and thus render
the preservation of the species more certain. The whole family of the
_Abdominalia_, a name proposed by Darwin, if I am not mistaken,
have the sexes separate; and the males, comparatively very small, 56
are attached to the body of each female. It is a case of polyandria
which we see realized in the _Scalpellum_. Darwin made known the
existence of supplementary males, so small and so little developed,
that they are with difficulty discovered, and so badly are they
provided with organs that they have neither those of motion nor a
stomach to digest. We have not exhausted the strange peculiarities of
this particular group; there are some which live without shells and
claws in the inside of other cirrhipedes, and atrophied males which
only exist at the expense of their own females.
It is almost useless to make the remark that more especially here
there exist almost insensible gradations of difference between
parasites, messmates, and free animals, and we shall find more than
one example of this in the crustaceans to which we now allude.
The most interesting fixed messmates are evidently those cirrhipedes,
which, under the name of _Tubicinella_, _Diadema_, or _Coronula_,
cover the skins of whales. They are, like all the rest, free in their
infancy, but soon they take shelter on the back or on the head of one
of these huge cetaceans, which they never quit when they have once
chosen their abode. That which gives them great importance is, that
each whale lodges a particular species; so that the crustacean
messmate is a true flag which indicates in some respect the
nationality, and it would not be without interest for voyagers who are
naturalists to study these living flags.
The great whale of the north, the _Mysticetus_, which our northern
neighbours discovered while seeking for an eastern passage to
India, a species which never leaves the ice, carries no cirrhipedes. 57
This fact was already known to Iceland fishermen of the twelfth
century. The intrepid whalers of these regions used to distinguish a
northern whale, without "calcareous plates," from a southern whale
with plates, that is to say, with cirrhipedes. This latter whale is
the celebrated species of temperate regions, the _Nord-Kaper_ which
the Basques used to hunt, from the sixth century, in the Channel, and
which they used afterwards to pursue even to Newfoundland. The whales
of the southern hemisphere, like those of the Pacific Ocean, all have
their own species of cirrhipedes. We found in the museum of the
Zoological Garden at Amsterdam, a _Coronula_, brought from Japan by
Mr. Blomhof, known under the name of _Coronulæ reginæ_, which, no
doubt, characterizes the whale of those latitudes. Another northern
whale, the _Keporkak_ of the Greenlanders, very remarkable for its
long fins, which give it the name of _Megaptera_, is covered very
early in its life with these crustaceans, so much so, that the
Greenlanders imagine that they are born with them. Some even have
pretended to have seen Megapteræ covered with these coronulæ before
their birth. Eschricht has in vain offered a reward to him who would
send him coronulæ still attached to the umbilical cord; he has only
received some pieces of skin covered with hairy bulbs. There is no
doubt that young whales have been seen and captured while following
their mother, which were already covered by these crustaceans.
Steenstrup has indicated the presence of _Platycyamus Thompsoni_ on
the body of the _Hyperoodons_, and the _Xenobalanus globicipitis_ on
the globiceps of the Shetland Isles.
The _Cryptolepas_ is a new genus of Coronulidæ which inhabits the 58
coast of California, on the singular mysticete recently distinguished
by the name of _Rhachianectes glaucus_. The _Platylepas bisexlobata_
has lately been observed on one of the Sirenia, the _Manatus
latirostris_. The marine turtles are also invaded by these singular
animals, and their peculiar form, joined to their habitat, has given
them the name of _Chelonobia_. It is not uncommon to find by the side
of these Chelonobiæ, and even upon them, the Tanaïs, Serpulæ, and
Bryozoariæ, forming together an animal forest on the cuirass of the
turtle. The _Matamata_, a turtle living in the brackish water of
Guiana, is covered with a cirrhipede more allied to the ordinary
balani than to the chelonobiæ. Other living reptiles are not more
exempt from cirrhipedes than turtles; the _Dichelaspis pellucida_ and
the _Conchoderma Hunteri_ invade different sea-snakes. Many sharks
harbour particular kinds, among which we mention the _Alepas_ of the
_Spinax niger_ from the coasts of Norway. The same Alepas has been
found on the _Squalus glacialis_ at the same time as the _Anelasma
squalicola_. Half a dozen varieties of these are known, one of which
inhabits an echinoderm, another a decapod crustacean. These kinds of
alepas are so reduced when they are adult, and are so completely
despoiled of their distinctive attributes, that it is necessary to
study them with especial care in their first dress, in order to
recognize their parentage.
Other cirrhipedes establish themselves on neighbours of their own
class, and we also find crustaceans upon other crustaceans. A pretty
genus lives near Cape Verd on the carapace of a large lobster, and
spreads itself on the centre of the back like a bouquet of flowers. My
son has procured some very fine specimens, an account of which he 59
will publish, together with the other materials which he has collected
during his passage across the Atlantic. Mr. John Denis Macdonald found
in abundance on the branchiæ of a crab in Australia, the _Neptunus
pelagicus_, which he places between the Lepas and the Dichelaspis.
The most singular, if not the most interesting of all these
cirrhipedes, are the Gallæ, which appear under the tail of crabs or
the abdomen of paguri, and which zoologists designate under the names
of _Peltogaster_ or _Sacculina_. They are found in both hemispheres.
The recurrent development is so complete, that we can no longer
distinguish any organic apparatus unless it be that of reproduction,
and the whole body is a mere case enclosing within its walls eggs and
spermatozoids. We see them very frequently under the abdomen of the
crabs of our coasts, or even on the segments of the bodies of paguri.
Mons. A. Giard has lately studied these animals. It is during the
coupling season, according to him, that the Peltogasters establish
themselves upon the crabs. Professor Semper has brought back quite a
collection of them from his voyage to the Philippine Islands, and has
entrusted them to one of his pupils, Dr. Kussmann, for the purposes of
study. We heard him with great interest, at the late Congress at
Wiesbaden, explain with remarkable clearness the results of his
learned and conscientious observations. We do not think that we shall
be wrong in adding that, for a long time, we shall see nothing better
or more complete on this subject. All those cirrhipedes which adhere
by their head to the skin of their host, by means of filaments, are
now designated by the name of _Rhizocephala_.
A curious opinion, quite recently expressed by a naturalist, Mons. 60
Giard, and which is a sign of the times, is that the Peltogaster of
the Pagurus has become a Sacculina on the crab; the host having been
transformed, its acolyte has done the same thing under the same
influence.
Professor Semper has also found among the Philippine Islands, isopod
crustaceans living as messmates after the manner of the peltogasters.
Two cirrhipedes of the family of Peltogaster, the _Sylon Hippolytes_
and the _Sylon Pandali_, have been found by Mons. Sars under the
abdomen of the _Pandalus brevirostris_.
There are cirrhipedes on the gasteropod molluscs. The _Concholepas
Peruviana_, that beautiful shell which has long been considered a
rarity in our collections, is frequented by the _Cryptophiolus
minutus_, only a sixth of an inch in length. The _Scalpella_ often
inhabit the Sertulariæ and other polyps; _Oxynasps_, _Creusiæ_,
_Pyrgomæ_, and _Lithotryæ_ inhabit corals. Certain kinds of sponges
are regularly invaded by the _Acastæ_ of Leach, eight species of which
are mentioned by Darwin. As we find elsewhere parasites on parasites,
here also we find messmates on messmates; on the common anatifa we
perceive other genera, and on the _Diadema_ of the North Pacific, we
almost always see _Otions_ and _Cineras_. The _Protolepas bivincta_
also, a fifth of an inch in length, lives as a messmate in the mouth
of the _Alepas cornuta_; and the _Elminius_ of Leach also inhabits
other cirrhipedes. The _Hemioniscus balani_, which Goodsir had taken
some years ago for the male of the Balanus, is a messmate on these
cirrhipedes. Parasites also are found in messmates; the soldier-crab
gives lodging to the sexual _Eustoma truncata_ in its interior. 61
A macrourous crustacean which we ought to mention here, the _Galathea
spinirostris_, Dana, frequents a comatula, the colour of which it
assumes; it is the same without doubt with the _Pisa Styx_, which
lives on a polyp known by the name of _Melitoea ochracea_.
If we pass from the crustaceans to the molluscs, we have to notice in
the first place an elegant gasteropod, the _Phyllirhoa bucephala_,
which carries on its head a singular appendage, the nature of which
has only lately been known; J. Müller took it at first for a medusa,
then he abandoned this opinion, when at length Mons. Krohn referred it
definitively to the lower polyps; it differs from its congeners only
by its form, its tentacular cirrhi, and its mode of life: it is the
_Mnestra parasites_. There are a great number of acephalous molluscs,
which we might mention as messmates, but we will only refer to the
_Crenellæ_ which are regularly found in the substance of sponges.
The _Philomedusa Vogtii_ of Fr. Müller, which lives on the _Halcampa
Fultoni_, undoubtedly deserves to be mentioned here as a fixed
messmate. Many bryozoa spread themselves over marine animals, and
often engage in a deadly struggle with their patron. But among all
these bryozoa we must mention an animal very common on the sea-shore
at Ostend, and which one would take for a dried leaf, the _Flustra
membranacea_. On the surface of these imitative leaves are found
little bouquets of other bryozoa, which are either _Crisiæ_ or
_Scrupocellariæ_. Another kind, which has also passed for a gelatinous
plant, bears the name of _Halodactylus_. Without any microscopic
study, one can obtain an idea of these colonies. One of these 62
Halodactyles spreads itself upon the stalk of a Sertularia, all the
inhabitants of which it stifles, so that it is the victim himself who
serves as a guardian to the invader.
These Halodactyli are very widely spread over the Northern Seas, and
often establish themselves on the large horse-hoof oyster. Michelin
has noticed under the name of parasite a fossil _cellepore_ from the
saltpits of Touraine and Anjou, which entirely surrounds the shell of
a gasteropod; in order to prevent its patron from dying of hunger, the
bryozoon develops itself around the mouth like a gallery, and prolongs
its last spiral. This _Cellepora parasitica_ has evidently a place
here.
Many of these messmate bryozoa are found in a fossil state in the crag
of the Antwerp basin.
We have still to mention among fixed messmates many polyps, some of
which are very remarkable. Thus, many naturalists speak of vast
colonies of polyps in which lodge various animals which shelter
themselves there like paguri in deserted shells.
Among these are the colonies of which Forster speaks, which are not
less than three feet in diameter, and fifteen feet in height, with a
crown of eighteen feet in diameter. Dana also makes mention of an
_Astræa_ of twelve feet in height, and of _Porites_ twenty feet high,
which contain more than five millions of individuals, among which a
number of animals come to take refuge.
The Museum of Natural History at Paris is in possession of a superb
specimen of _Porites conglomerata_: in the middle of the colony lodges
a Tridacna (_Trid. corallicola_, Val.) like a pagurus under a forest
of hydractiniæ. This remarkable polyp was brought from the Seychelles
Islands by Mons. L. Rousseau. It is not impossible that pinnotheres 63
live in this same tridacna, and that we have there a fresh example of
messmate within messmate.
In the Bay of Massachusetts, on the coast of New England, another
curious messmate lives at great depths; Dana has lately described it,
under the name of _Epizoanthus Americanus_, V. It establishes itself
in the _Eupagurus pubescens_. The _Sertularia parasitica_ of the gulf
of Naples, from which I have formed the genus _Corydendrium_, is a
messmate after the manner of an infinite number of other polyps. In
closing this list, we shall mention a polyp, named _Halicondria
suberea_, and the _Actinia carcinopodus_ of Otto, which inhabit an
univalve mollusc; as also the _Heterosammiæ_ and the _Heterocyathi_ of
the family of Turbinolidæ, which lodge in a trochoid shell.
The sponges, placed by naturalists by turns among plants or on the
confines of the animal kingdom, are now generally regarded as polyps;
this is the opinion expressed by Haeckel, who wishes at the same time
to replace the term Coelenterata by that of Zoophytes. The learned
naturalist of Jena, when making this proposition, should have
remembered that in 1859 we placed the sponges in the group of polyps,
as the lowest in the scale; and that we proposed, from the time when
the acalephæ were recognized to be adult polyps, to designate all
these animals under the name of Polyps. Some time after, R. Leuckart
proposed the appellation Coelenterate Polyps, which has been generally
received. Professor Haeckel would have lost nothing by acknowledging
that in 1873 he arrived at a result similar to that to which I had 64
come twenty years before, and that it is not a very happy innovation
to change the term polyps for zoophytes. It is the more surprising
that this naturalist has forgotten to quote my opinion, since at the
congress of naturalists at Hanover in 1866, I had placed this question
on the agenda for an ordinary meeting.
I maintained, in opposition to the opinion of the naturalists whose
authority had been especially recognized in the matter (Osc. Schmidt,
who was present, among others), that sponges are lower polyps, whether
they are regarded as to their development or their organization.
This group, so remarkable in form, so varied in colour and appearance,
very often affords examples of animals which live with them as true
messmates; and we find the same relations established between them in
both hemispheres. As we observe rhizophales on crabs and soldier-crabs,
and pinnotheres on bivalve molluscs, so we find that the sponges of
the Indian Seas or of Japan harbour the same messmates which we
discover on them in the Northern Seas or the Atlantic.
In the sea of Japan is found a very remarkable sponge, generally known
by the name of _Hyalonema_. It is a bundle of spicules like threads of
glass, which seem artificially tied together, and on the surface of
which we regularly find a polyp of the genus _Polythoa_. The nature of
this sponge, and its relations with the polyps which surround it, have
been discussed for many years. Ehrenberg had recognized the polyp
Polythoa around the spicules, but the Hyalonema was considered by him
as an artificial product. The _Polythoæ_ were regarded as only a case
in which had been placed this bundle of spicules. The learned
microscopist of Berlin had even thought that he had found the proof 65
of this opinion in the presence of woollen threads which were observed
in a specimen which Mons. Barbosa du Bocage had sent him from Lisbon.
Woollen threads had indeed adhered to the spicules of Hyalonema, but
they came from the fishermen, who, when they drew these sponges from
the water, placed them carefully in their bosoms under their woollen
jerseys.
Dr. Gray, of the British Museum, considers the sponge as a parasite of
the Polythoa, and that the bundle of spicules belongs, not to the
sponge, but to the polyp. The most learned naturalist on the subject
of sponges, Mr. Bowerbank, expresses a different opinion. The sponge
and its spicules, according to him, are but a single body, and the
polyps are only a part of it. The supposed polyps would only form a
cloacal system for the use of the sponge colony.
Valenciennes, guided no doubt by the observations of Philippe Poteau,
was the first to recognise the nature of the sponge and its spicules,
but it is to Max Schultze that we must give the credit of
distinguishing the true character of this extraordinary marine
production. He has shown that the bundle is formed by the
extraordinarily long spicules of the sponge, and that the polyp
establishes itself upon it, by forming a sheath around the bundle.
The fact is no longer doubted by any one, that the long spicules form
part of the sponge, and that the polyp establishes itself on a part of
the colony. But science rarely advances by a single stride, and Max
Schultze, like his predecessors, mistook the top of the sponge for 66
the bottom; Professor Loven has shown the true pose of the Hyalonema,
and this he has effected by means of a small specimen from the
Northern Sea.
Semper found a new OEga, to which he gave the specific name of
_Hirsuta_, in an enlarged canal of the new Hyalonema of the Philippine
Islands, which he dedicated to Mons. Schultze.
The Adriatic also produces a species of the same genus (_Polythoa_)
which inhabits, like that of the Chinese Sea, a sponge to which the
name of _Axinella_ has been given. These Polythoæ are only found on
the Axinellæ, says Osc. Schmidt, who has especially studied the
sponges of this sea and of the Mediterranean. Professor Gill mentioned
at the last meeting of the scientific congress at Portland (1873), a
new Hyalonema found on the coast of North America by the fishery
commission of the United States. A memoir on these sponges,
interesting in a systematic point of view, is due to the pens of
Herklots and of Marshall.
[Illustration: Fig. 1.--Ophiodendrum abietinum on Sertularia abietina.]
We think that we ought to place among fixed messmates a very
problematical organism which lives on Sertulariæ, especially on the
_Sertularia abietina_, and which Strethill Wright has designated
by the name of _Corethria sertularia_. Claparède has given to
this singular animal the more expressive name of _Ophiodendrum
abietinum_.
We have regularly found it on the _Sertularia abietina_ at Ostend, 67
every time that we have had an opportunity of observing these polyps
immediately that they have been raised from the bottom of the sea. It
is an organism whose affinities are not yet established.
CHAPTER IV. 68
MUTUALISTS.
In this chapter we bring together animals which live on each other,
without being either parasites or messmates; many of them are towed
along by others; some render each other mutual services, others again
take advantage of some assistance which their companions can give
them; some afford each other an asylum, and some are found which have
sympathetic bonds which always draw them together. They are usually
confounded with parasites or messmates.
Many insects shelter themselves in the fur of the mammalia, or in the
down of birds, and remove from the hair and the feathers the pellicle
and epidermal _débris_ which encumber them. At the same time they
minister to the outward appearance of their host, and are of great
utility to him in a hygienic point of view.
Those which live in the water have other guardians: instead of
insects, we find a number of crustaceans which establish themselves on
fishes, and if there are no scales of the epidermis which annoy them,
there are mucosities which are incessantly renewed in order to protect
the skin from the continual action of the water.
We find many on the surface of the scales, and others which conceal 69
themselves at the bottom of mucous canals. We have brought together
only a few examples, and there are certain others which are mentioned
elsewhere, but which ought more properly to be placed here.
The insects long known under the name of _Ricini_, and to which
many other appellations have been given, deserve to figure in the
first rank in this group. They have always perplexed entomologists,
who seem to consider them as parasites allied to acaridæ and lice. It
has, however, been long known that they have no trunk to suck with,
and that they have two small scaly teeth, which rather serve for the
purpose of biting. A long time since, the examination of their stomach
proved that they contain only morsels of skin instead of blood. This
has induced many entomologists to place them in the same order as
grasshoppers, that of Orthoptera.
Lyonet has given figures of several of those which he studied with the
care which he so well knew how to employ in his anatomical
investigations; and in 1818 Nitzsch, a professor at Göttingen, had
brought together so great a number of them, that it required several
days to examine his collection; he began the publication of his
catalogue, but has not had time to finish it. Several other
entomologists and anatomists have since taken up the subject.
We owe the description of several hundred species to Mr. Denny. Mons.
F. Rudow has lately made known a great number of species which he has
collected from the skins of birds coming from Japan, Australia, 70
Africa, and the two Americas.
Professor Grube, of Breslau, has published the description of the
insects and acaridæ found during the travels of Middendorf in Siberia.
These descriptions relate especially to the Philopteræ of birds, the
Pediculinæ of the mammalia, a flea of the _Mustela Siberica_, and an
acarus of the _Lemmus_. Quite recently, an American naturalist, Mr.
Packard, who has undertaken the study of so many different subjects,
has published in the "American Naturalist" the description,
accompanied by an engraving, of the _Menopon picicola_, found on the
_Picoides Arcticus_ from the lower Geyser basin, Wyoming territory,
also of the _Goniodes Merriamanus_, the _Tetrao Richardsoni_, and the
_Goniodes mephitidis_, found on a _Mephitis_ from Fire-Hole Basin,
Wyoming territory; of the _Nirmus buteonivorus_, from a _Buteo
Swainsonii_; and of _Docophorus Syrnii_, from _Syrnium nebulosum_.
A great number of these insects live between the feathers of birds,
and can be more easily observed, since they detach themselves after
the death of their host. They are easily found on the skins of birds
prepared for museums. These ticks form a family under the name of
_Riciniæ_, and this family is divided into two parts, the _Liotheidæ_
and the _Philopteridæ_.
Among the many generic divisions, one of the most interesting has
received the name of _Trichodectes_; it contains twenty species, one
of which lives on the dog, another on the cat, another on the ox; in a
word, we discover a distinct species on each of the domestic mammals.
It has been said that the _phthiriasis_ of the cat is occasioned by 71
the abundance of ricini. The trichodectes of the dog has lately
attracted the especial notice of naturalists, and that from the
following circumstances.
There is no tape-worm more common in the dog than the _Tænia
cucumerina_. But whence comes it? How is it introduced? This had been
an enigma for many years, at the time when I dissected some dogs
infested with _Tænia serrata_, in the Museum of Natural History at
Paris. Together with the _Tænia serrata_, the number and age of which
I knew beforehand, since I had myself _planted_ them, there were found
in the intestines of one of the dogs some individuals of the _Tænia
cucumerina_. My dogs had taken nothing but milk, and _cysticerci
pisiformes_. Were there cysticerci of different kinds in the
peritoneum of the rabbit? The veil is now withdrawn. We have just said
that the dog harbours a tick known under the name of Trichodectes, and
in this trichodectes lodges the Scolex, we might even say the larva of
the _Tænia cucumerina_. Dogs, especially young ones, lick their hair
continually, and it is by this operation that the young tænia is
introduced. It is by a similar process that the horse introduces the
eggs of the OEstrus which are hatched in its stomach.
Many of these ticks live abundantly in birds, and multiply rapidly.
The _Liothe pallidum_ lives on the cock, the _Liothe stramineum_ on
the turkey, the _Philopterus falciformis_ on the peacock, the
_Philopterus claviformis_ on the pigeon. It is to be observed that
every bird can nourish many different kinds. Fig. 2 represents the
tick which infests the sea-eagle, called Pygarg.
[Illustration: Fig. 2.--Ricinus of the Pygarg.] 72
Fishes harbour crustaceans instead of ticks, and their number is not
less considerable than on mammals and birds. These crustaceans have
perplexed naturalists more than once, because they could only regard
them as parasites. They live on the produce of cutaneous secretions,
and if they improve, as do the ticks, the cleanliness of their host,
they are not less useful in a hygienic point of view, for they prevent
the accumulation of cutaneous productions.
Among these crustaceans, we must mention the _Caligi_ and the
_Arguli_, which never become bloated, the _Ancei_, and probably other
genera. Instead of the ungainly and unusual forms of true parasites,
they all preserve, together with their fishing tackle and locomotive
apparatus, their neat and elegant appearance. The sexes even differ
only in size. They remain during the whole of their life what they are
at the beginning; that is to say, charming in form, with a
delicately-shaped corselet, numerous and slender claws, and are as
graceful in their movements as when in a state of rest. The greater
number of osseous fishes lodge Caligi on the surface of their skin.
These fix themselves by means of strong cables, but without
sacrificing their liberty. They are usually called fish lice.
Fishermen, when returning from the northern fishery, generally find
their vivarium full of these graceful vermin. It may be said that 73
the caligi are common everywhere, and that each species has its own
caligi. The fishes of the family Plagiostoma, notwithstanding the
hardness of their skin, afford food to some of these; they multiply so
rapidly sometimes, that they cover their host as though they took the
place of scales. The cod gives lodging to a charming species of a very
beautiful shape, which in its turn, affords a resting-place to the
Udonella. It is always attached to the ovisacs, and doubtless plays
the same part as the Histriobdellæ, so that we shall find the Caligi
attending to the toilet of the cod, and the Udonellæ in their turn
waiting on the Caligi.
[Illustration: Of the natural size.]
[Illustration: _Caligulus elegans_ (fem.)]
The name Arguli has been given to some crustaceans which resemble the
caligi in size and in manner of life, and which principally frequent
fresh-water fishes. The _Argulus foliaceus_ is the name of the
species which has been known for the longest time, and which is most
extensively found. It is to be seen on our pikes, carps, sticklebacks, 74
and on the greater part of our river fish. Mr. Thorell, in his
monograph, mentions twelve species of Arguli proper, and four species
of which he composed the genus _Gyropeltis_. Four are found in Europe,
two of which are on salt-water, and two on fresh-water fish.
Quite recently, Professor Leydig has made known another species living
on the _Phoxinus levis_. Arguli are met with on the fishes of Africa,
the Indies, and North and South America. Like the caligi, these
animals spontaneously abandon one host, to go and attend to the toilet
of another.
Another animal, which has been taken for a Lernæan, deserves to take
its place by the side of the Caligi, at least on account of its manner
of life. We refer to that singular being which Leydig discovered in
1850 in Italy, while studying the mucous canal of a _Corvina_, at
Cagliari, and to which he gave the name of _Sphoerosoma_. To judge by
the plate and by some details, this _Sphoerosoma_, the name of which
ought to be changed to _Leydigia_, belongs, if we mistake not, to the
same group as the Histriobdellæ. We are persuaded that the first
opportunity will confirm the correctness of this alliance, by the
study of its embryonic form. If we had not been able to examine into
all the development of the Histriobdellæ, more than one naturalist
would have considered them Lernæans, as happened at the congress of
German naturalists at Carlsruhe.
If we see many of these crustaceans live a joyous life while young,
there are others which seem to practise economy, and to emancipate
themselves when they have grown old. Mons. Hesse and Mr. Spence Bate a
few years since revealed the secrets of their existence.
Naturalists had recognized some crustaceans under the name of 75
_Ancei_, and others under the name of _Pranizæ_, living together upon
fishes, but with very different organs for fishing and swimming.
M. Hesse, curious to know the manner of life of the Pranizæ, made
observations on them in a small aquarium, and he perceived that the
parts of the mouth were all at once transformed into formidable
mandibles, which caused them to resemble Ancei. As it had often
occurred with respect to other groups, that the same crustacean at
different periods of its evolution had been taken for different
animals, the naturalist of Brest had some suspicion as to their
identity, and soon ascertained by direct observation that he had not
been mistaken. The Pranizæ become Ancei, and live upon fishes under
their first form, like caligi and arguli. Nothing can be seen which is
more curious than these crustaceans, which ride on the back or the
sides of fishes, and assume there every possible attitude.
The Pranizæ fix themselves in the mouth and in the gills as well as on
the skin. Some are found on sharks as well as on osseous fishes. They
fear neither heat nor light, and do very well under damp sea-weed
while waiting for the return of the tide. They run and swim with the
same facility. When in the condition of Ancei, they lose their
agility, and, under this form, all denotes their sedentary habits.
They appear to live in holes, at the bottom of which they defend
themselves with their powerful mandibles. It has been observed that
fecundation is accomplished, as in the _Axolotls_, before the
evolution is complete, but that the eggs are not laid until the animal
assumes the form of Anceus.
We may here remark that the change of appearance takes place only 76
among the females; the males preserve their dress and their liberty.
Some naturalists assert that we must not accept the metamorphosis of
either sex as an established fact, except for the purpose of
arrangement. All, however, tends to show that Mons. Hesse has fairly
interpreted facts; but it appears to us probable that the whole of the
history of these strange crustaceans is not fully known.
Fishermen have long since known whale-lice, the _Cyami_ of
naturalists, of which we have already made mention while speaking of
free messmates. They live at liberty on the skin of their host, and
multiply with extreme rapidity. These Cyami have a regular form, but
completely different from the others, and have given (like the Ricini
and the afore-mentioned crustaceans), great trouble to systematic
zoologists. The place which they ought to occupy is far from being
definitely fixed. At all events they may be considered as a shorter
kind of Caprellæ.
As each whale has cirrhipedes which are peculiar to itself, so each
has its own cyami. Professor Lütken, of Copenhagen, has made known ten
or twelve species, all found on cetacea, in the two hemispheres. The
supposed Cyamus, represented by Dr. Monedero as living on the Biscayan
whale, is a Pycnogonon.
The Anilocræ and the Nerocilæ, like the Cyami and other genera,
establish themselves on the back of a fish which is a good swimmer.
Jealous of their liberty, they preserve their oars and their fins, in
order to change their convoy, when the desire seizes on them, and do
not imitate the Bopyrians, which instal themselves on the narrow 77
branchial cavity of some decapod crustacean, and as soon as they have
entered, throw off all their travelling baggage; in fact, there is no
other means for them to gain admission; their lot is identified with
that of their host; they can no longer live without him. The female
only, it is true, thus renounces her liberty; she sacrifices herself,
as usual, for her family, while the male, far from giving himself up,
preserves his defensive arms, his claws, and his liberty.
The crustaceans called Caprellæ are perhaps not so independent as they
appear to be; it is not impossible that their place may be among the
crustaceans now under our consideration. They are often found,
together with the Tanaïs, on the bodies of cetaceans and chelonians,
on plagiostomous fishes, or in the midst of colonies of Sertulariæ.
They also establish themselves on buoys when they are well covered
with animal life; and we have discovered them in prodigious numbers on
a piece of cable which had lain at the bottom of the sea, and the
whole surface of which was covered with animals of every kind.
We may here mention the Pycnogonons, the Saphyrinæ, the Peltidiæ, and
the Hersiliæ; these crustaceans often crawl over the skins of their
congeners, but without ever renouncing their independence; and they
are all more or less occupied with the toilet of their neighbours.
We shall place in a second section some animals which have been
usually classed among parasites, rather because of their living upon
their neighbours than on account of their mode of life. If it is
necessary in menageries to have keepers to cleanse the animals
themselves, it is as requisite to have others to keep the cages 78
clean, and to remove dung and filth. Many animals perform this office.
The rectum of frogs is always literally full of _Opalinæ_ which
swarm in this cavity, like ants in their ant-hill, and doubtless live
on the contents of the intestine.
These Opalinæ are true infusoria, which do not wait till the fecal
matters are decomposed, and till the waters are corrupted by their
presence; they prevent accidents which might arise, and interfere in
time to purify the water from these excretions. There have been found
hitherto in the rectum of frogs, and in the different annelids, the
Pachydrili, the Clitelides, the Lumbriculi, and the Enchytrei. We have
also seen them in the Planaria and the Nemertians. There is no sight
more curious for those who are commencing microscopical studies, than
the examination of the contents of the rectum of these Batrachians.
Van Leeuwenhoeck knew, two hundred years ago, those animalculæ, to
which Bloch at a later period gave the name of _Chaos intestinalis_.
There are also some Rotatoria, the _Albertiæ_ for example, which ought
to have a place here, and which Dujardin has described and named. They
live in the intestines of the Lumbrici and of snails, and in the larvæ
of Ephemerides.
Dujardin first pointed out the _Albertia vermiculus_; since then Mons.
Schultze has made known the Albertia of the _Näis littoralis_, and
Radkewitz has recognized in the small worm of our gardens the
_Enchytreus vermicularis_. Long since, Siebold correctly stated that
these animals are not parasites, since they do not live at the expense
of their host.
There is a worm in the Philippine Islands, as Professor Semper has 79
informed me, which lodges in the intestines of a fish, with its head
usually projecting outwards, and which watches the crustaceans
attracted by the excreta of its host; but although it chooses the
intestine of its neighbour as a place of shelter, it is not a
parasite.
Fishermen affirm, and the examination of the animal's stomach confirms
their assertion, that the _Cyclopterus lumpus_ feeds on nothing
but the excreta of other fishes. Indeed, it is not possible to count
the number of intestinal worms known by the name of _Scolex_, which
are found in the contents of the stomach and the intestines. Besides
this, we have long known the peculiarities of some insects which
cannot live except on the dung of certain animals; and there is an
example of one of these insects, found in a fossil state, which
anticipated the discovery of the remains of an extinct mammal before
unknown in that district. The larvæ of the fly _Scatophaga
stercoraria_ live only on excrementary matter.
There are also nematode worms which exist under these conditions, and
which develop and propagate their species in the intestines as if in
the midst of damp earth. The small eel-like creatures so abundant in
cow-dung propagate in it; they are not parasites, and are allied to
those of which we speak in this chapter.
Besides those attendants which busy themselves about the cleanliness
of other animals, we find some whose duties are less extensive, and
whose cares are more limited. Many animals produce a greater number of
eggs than they can bring to perfection, and those which are decomposed
for want of fecundation, or which die in the course of evolution, 80
are under the care of an especial attendant, employed to make away
from time to time with the addled eggs, or the embryos that have
failed to come to maturity.
In this manner lobsters give lodgings in the midst of their eggs to a
worm, which we at first took for a Serpula, and which, after a
complete examination, turns out to be one of the Hirudinidæ: we have
given it the name of _Histriobdella_. It is as singular in its
movements as in its conformation, and its manner of living approaches
that of the _Pontobdellæ_ of the rays, of which we shall speak
subsequently. We announced this discovery a few years ago in the
following terms:--
It is known that lobsters, as well as crabs and the greater part of
the crustacea, carry their eggs under the abdomen, and that these eggs
remain suspended there till the embryos are hatched. In the midst of
them lives an animal of extreme agility, which is perhaps the most
extraordinary being which has been subjected to the eyes of a
zoologist. It may be said, without exaggeration, that it is a biped,
or even quadruped, worm. Let us imagine a clown from the circus, with
his limbs as far dislocated as possible, we might even say entirely
deprived of bones, displaying tricks of strength and activity on a
heap of monster cannon balls, which he struggles to surmount; placing
one foot formed like an air-bladder on one ball, the other foot on
another, alternately balancing and extending his body, folding his
limbs on each other, or bending his body upwards like a caterpillar of
the geometridæ, and we shall then have but an imperfect idea of all
the attitudes which it assumes, and which it varies incessantly.
Its rank and its affinities would have given rise to long discussions 81
if we had not made known at the same time its evolution and anatomical
structure.
It is neither a parasite nor a messmate; it does not live at the
expense of the lobster, but on one of the productions of these
crustaceans, much in the same manner as do the Caligi and the Arguli.
The lobster gives him a berth, and the passenger feeds himself at the
expense of the cargo; that is to say, he eats the eggs and the embryos
which die, and the decomposition of which might be fatal to his host
and his progeny. These Histriobdellæ have the same duty to perform as
vultures and jackals, which clear the plains of carcases. That which
causes us to suppose that such is their appropriate office, is that
they have an apparatus for the purpose of sucking eggs, and that we
have not found in their digestive canal any remains which resemble any
true organism. We find the feces, rolled up as balls, placed after
each other in their intestines.
The crustaceans also feed other Hirudinidæ. Mons. Leydig has noticed a
_Myzobdella_ on the _Lupa diacantha_. The fresh-water crab, common in
all the rivers of Europe, nourishes two, the _Astacobdella roeselii_,
which lives under the abdomen, or about the eyes, and the
_Astacobdella Abildgardi_ which especially frequents the branchiæ. Two
astacobdellæ on the same crab doubtless play different parts. We
should almost venture to assert, _à priori_, that the species in the
gills lives as a parasite on the blood of its host, whilst the other,
lodged under the abdomen, plays the same part as the histriobdella of
the lobster.
We often find among the eggs of the ordinary crab of our coasts 82
(_Cancer moenas_) a nemertian which probably performs the same
office. He is lodged while young in a kind of firm sheath attached to
the abdominal processes. We have been able easily to study the first
phases of its evolution. We have given it the name of _Polia
involuta_.
This nemertian had been observed at Messina, and described before by
Kölliker under the name of _Nemertes carcinophilus_, and it has
just been described and figured anew by Mr. M'Intosh, in a monograph
of British annelids published by the Ray Society.
The sturgeon seems to give lodging in its eggs to a polyp which plays
the same part. In fact, Mons. Owsjannikoff, at the congress of Russian
naturalists at Kiew, described an animal, _Accipenser ruthenus_,
which lives in the eggs of the sterlet. Some eggs placed in water for
a few hours at first show tentacles on the outside, then a whole
colony, and each part consists of four individuals, which have a
common digestive cavity, resembling somewhat a hydra divided
longitudinally in four. Each has six tentacles, two of which are
terminated by transparent corpuscles, perhaps nematocysts; the
digestive cavity extends into the arms, as in the hydra; the mouth is
not between the tentacles, but at the opposite pole. They are not all
lodged within the eggs; some are found outside, according to the
observations of Mons. Koch. Does not this animal fulfil in the egg of
the sterlet, the same office as the histriobdella in the egg of the
lobster?
The eggs of some insects are attacked by very little ichneumons, the
_Proctotrupidæ_; they empty them, and then instal themselves in
the shell. Mons. Fabre has mentioned, in his memoir on the habits of 83
the _Meloë_, a worm found in an egg.
M. Barthelemy has studied a nematode worm (_Ascaroides limacis_)
which inhabits as a parasite the egg of the grey snail; is this not
the ordinary worm of the snail which has introduced itself into the
eggs?
Many animals establish themselves on their neighbours, not to obtain
any advantage from them, except to profit by their fins; they are not
themselves sufficiently adapted to rapid motion, so they seize a good
courser, mount on his back, and ask from him only a resting-place and
no provisions. But it is often very difficult to say where
commensalism ends and mutualism begins; the cirrhipedes, for example,
establish themselves on a piece of floating wood, or on the bottom of
a vessel; on a block of stone, or on one of the piles of a groin; on
an immovable animal as well as on a good swimmer.
Some fourteen years ago, Jacobson of Copenhagen wrote an interesting
essay, to show that the young bivalves that are found in the branchiæ
of anodonts at a certain period of the year are parasitical animals,
for which he proposed a new name. But these supposed parasites are
only young anodonts, which by the help of a very long cable, which
proceeds from their foot like a byssus, attach themselves to their
mother, or to a fish which will carry them to a distance.
We see full-grown acephalous molluscs, as mussels and pinnæ, still
keep these cables, under the name of byssus, during their whole life.
There are also among distomians, worms which though they are
hermaphrodite, couple two and two, and have this additional
peculiarity, that while one increases rapidly the other becomes 84
atrophied.
An Egyptian distome, which lives in man, gives an instance of this
peculiarity, as well as the _D. filicolle_, which inhabits a fish
(_Brama Raii_). The caligi which live on the skin of fishes are,
when young, fastened by a cord which comes from the anterior edge of
their carapace: while quite little, they put themselves under the
protection of a kind neighbour, and allow themselves to be led by him.
The new tubularia, which we have dedicated to our learned colleague
Dumortier, often fixes itself on the carapace of ordinary crabs, and
causes itself to be conveyed like the Echeneis; the tubulary observed
by Gwyn Jeffreys, close by the eye of the _Rossia papillifera_, a
cephalopod mollusc, perhaps belongs to the same species.
Every colony of campanulariæ or sertulariæ lodges a crowd of messmates
and mutualists; and there are a great number of crustaceans and polyps
of all sizes which serve as an abode for infusoria of every kind. Some
establish themselves on the carapace or on the swimming appendages, as
in a carriage; others on one of the gills, which renders their mode of
life more easy, and the danger less great. An amphipod very
extensively spread over our sea-coasts, the _Gammarus marinus_,
usually has its appendages covered with _Vayinicola crystallina_.
CHAPTER V. 85
PARASITES.
"En plongeant si bas dans la vie, je croyais y rencontrer
les _fatalités physiques_, et j'y trouve la justice,
l'immortalité, l'espérance."--MICHELET, _l'Insecte_.
The parasite is he whose profession it is to live at the expense of
his neighbour, and whose only employment consists in taking advantage
of him, but prudently, so as not to endanger his life. He is a pauper
who needs help, lest he should die on the public highway, but who
practises the precept--not to kill the fowl in order to get the eggs.
It is at once seen that he is essentially different from the messmate
who is simply a companion at table. The beast of prey kills its victim
in order to feed upon his flesh, the parasite does not kill; on the
contrary he profits by all the advantages enjoyed by the host on whom
he thrusts his presence.
The limits which separate the animals of prey from the parasite are
usually very clearly marked; yet the larva of the ichneumon, which
eats its nurse, piece after piece, resembles a carnivorous animal as
much as a parasite. There are indeed certain animals which take
advantage of the good condition of their Amphitryon, but which 86
render to him in return precious services. Thus those which live on
the produce of the secretions, or which clear the system of useless
materials in exchange for the hospitality which they receive, are not
true parasites. These services are of a very different character, and
the duties which they sometimes perform for each other are in some
respects analogous to medical care.
Every animal has its own parasites, which always come from without.
With some few exceptions, they are introduced by means of food or
drink. In order to ascertain their origin, the naturalist must
beforehand study the food, that is to say, the prey or the plant which
furnishes the habitual nourishment of the host which gives them
shelter.
A carnivorous animal, however, does not in general content himself
with a single kind of prey--one voracious animal of this class devours
all that comes in its way; another, more of an epicure than a glutton,
chooses with more discernment. But in the midst of this varied kind of
food there is always some species which forms the staple of the usual
bill of fare, and it is necessary to find out what this is if we wish
to ascertain the parentage and the metamorphoses of the parasite,
since it is that which conducts the parasite to its new destination.
The mouse is destined to the cat, and the rabbit to the dog; in the
same manner, each one of the herbivora is intended to be the prey of a
carnivorous animal, if not larger and stronger than itself, at least
more cunning. It is of great importance to discover the animal which
conducts the new-comer into his habitation. When we know it, we have
only to introduce into it the stranger guest, that sooner or later 87
he may pass into the body of his accustomed Amphitryon. In order
thoroughly to know these sedentary or vagabond populations, we must
not only study them at the different periods of the year, and under
all the conditions of their irregular life, but it is necessary to
follow them from the moment that they quit the egg till their complete
evolution, closely noticing all that relates to their reproduction.
In the dung of the cow, by the side of the elegant _Pilobolus_,
live masses of small eels, born in the stomach of the animal, which
wind and twist like microscopical serpents, and do not seek the
slightest help from the organ which shelters them. They are hatched in
the interior of the stomach, as if it took place in the meadow. These
little eels have evidently only the appearance of parasites, and it
may be that they render some service in some of the organs through
which they pass. This may also be the case with those which live on
the feces of others, or which, lodged in the rectum, watch for the
prey which is attracted by the odour. These, especially the latter,
are rather messmates than parasites. True parasites are animals
entirely dependent on their neighbours, unable to provide for
themselves, fed entirely at the expense of others. It is generally
supposed that parasites are exceptional beings, requiring a place by
themselves in the animal hierarchy, and knowing nothing of the world
except the organ which shelters them. This is an error. There are few
animals, however sedentary they may be, which are not wanderers at
some period of their lives, and it is not even uncommon to find some
which live alternately as noblemen or as beggars. Many of them only
deserve to be placed among paupers when they are in their infancy or 88
at the approach of adult age, for they only seek for help at the
beginning or towards the end of their career. These are very numerous,
and more than one species change their dress so completely that they
can no longer be recognized. Finding with their host both food and
lodging, they throw off their fishing and travelling gear, settle
themselves comfortably in the organs which they have chosen, and
having got rid of the baggage which connected them with the outer
world, preserve only their sexual organs.
As to the rank which these parasites occupy in the scale of being, it
may be said that there is no especial class of parasites; and worms
are not distinguished in this respect, except by having a greater
number of species subject to this rule. All classes among invertebrate
animals include parasites.
It is also an error to suppose that the whole species, the young as
well as the old, the males as well as the females, are always
parasites; often the female, not being able to provide for the
necessities of life, seeks for food and shelter, while the male
continues his nomad life. Therefore the female alone puts on the
pauper's dress, and by a recurrent development, assumes sometimes such
a singular appearance that the male no longer resembles her. One
cannot say that the females constitute the _beau sexe_ in this
group, since they are often so monstrous in form and size that their
appearance has nothing in common with a perfect animal; their body is
deprived of all its exterior organs, and there often remains only a
skin in the form of a leather bag, without any distinguishing
character.
What is still more astonishing, is to meet with males which, under the 89
conditions to which we have just alluded, come at last to seek for
assistance from their own female, so that she has to provide for all;
and the charitable animal which comes to her help takes the whole
family under his charge. Assistance is thus thoroughly organized in
the lower world; neighbours are found which serve as a _crèche_
for the indigent when they first quit the egg, others as a hospital
for the infirm adults or the females, and others again play the part
of innkeepers for all, instead of affording a place of refuge for some
privileged individuals.
There are but few animals, if indeed there are any, which have not
their peculiar parasites. Of all the fishes of our coasts we have
never found but one which had none; and perhaps, could we observe this
fish in different latitudes, we might find that it had its poor
dependants as well as the rest.
Thus we may assume that no animal is free in this respect, and man
himself regularly affords hospitality to many of them. We feed some
with our blood and our flesh; there are some which lodge on the
surface of our skin, others in the interior of our organs; some prefer
to establish themselves on children, others on adults. The name alone
of some is sufficient to make us shudder, while others live peaceably
in some crypt, without our suspecting their presence. Who is there
that does not nourish some acari, of the genus _Simonea_, in the
membrane of the nose? In fact, man gives a home to some dozens of
parasites, and the presence of the most terrible among them
constitutes, in certain countries, a condition of health which is
envied. The Abyssinians do not consider themselves in good health, 90
except when they nourish one or many tape-worms.
Among the animals to which man gives his involuntary assistance, we
may mention first, four different Cestoidea, or tape-worms, which live
in the intestines; three or four Distoma, which lodge in the liver,
the intestines, or the blood; nine or ten Nematodes, which inhabit the
digestive passages or the flesh. There are also some young Cestodes,
named _Cysticerci_, _Echinococci_, _Hydatids_, or _Acephalocysts_,
which find in him a _crèche_ to shelter them during their life. These
always choose enclosed organs, like the eye-ball, the lobes of the
brain, the heart, or the connective tissue. We also provide a living
for three or four kinds of lice, for a bug, for a flea, and two
ascarides, without mentioning certain inferior organisms which lurk in
the tartar of the teeth, or in the secretions of the mucous membrane.
There are some animals which harbour few inhabitants, while there are
others that keep up a great retinue; and it is not always, as we have
already said, that those who give lodging to but few enjoy the most
excellent health. We might give as an instance of this, a fish which
is known to all, the turbot, which as well as the woodcock is highly
prized, though both have their intestines literally obstructed by
tape-worms and their eggs. We have never opened one, large or small,
lean or fat, which had not its intestines filled with cestode worms.
They are so numerous as to form a kind of cork, which one might think
intended to close the passage of the pylorus.
Some authors give remarkable instances of the abundance of parasites.
Nathusius speaks of a black stork, which lodged twenty-four _Filariæ 91
lobatæ_ in its lungs, sixteen _Syngami tracheales_ in the tracheal
artery, besides more than a hundred _Spiropteræ alatæ_ within the
membranes of the stomach, several hundreds of the _Holostomum
excavatum_ in the smaller intestine, a hundred of the _Distoma ferox_
in the large intestine, twenty-two of the _Distoma hians_ in the
oesophagus, and a _Distoma echinatum_ in the small intestine. In spite
of this affluence of lodgers the bird did not appear to be in the
least inconvenienced.
Krause, of Belgrade, mentions a horse two years old, which contained
more than five hundred _Ascarides megalocephalæ_, one hundred and
ninety _Oxyures curvulæ_, two hundred and fourteen _Strongyli armati_,
several millions of _Strongyli tetracanthi_, sixty-nine _Tæniæ
perfoliatæ_, two hundred and eighty-seven _Filariæ papillosæ_, and six
_Cysticerci_. When we consider how many eggs a single worm produces,
we can understand how it is that so few animals escape being invaded
by them.
Sixty millions of eggs have been counted in a single nematode, and in
a single tape-worm, or rather in a colony, even a thousand millions of
eggs. Even the very animals which live as parasites, harbour others in
their turn. We find parasites on parasites, as we find messmates upon
messmates. Almost all writers on this subject give examples of these;
some in the larvæ of ichneumons, others in the lernæans, and we have
more than once met with nematodes in different crustacea still
attached to their host.
In order to understand thoroughly the living furniture of an animal,
especially of a fish, it is necessary to examine it while young; the
feces are the _Kitchen-middings_ of the stomach; it is from them 92
that we can appreciate the bill of fare of each. This study of the
food will one day excite much interest, not only in a scientific point
of view, but also with reference to fishing as an occupation.
There are some animals which are infested at every period of their
life, and at every season; others in far greater number only during
their youth, and they gather in at the commencement of their life the
harvest for the rest of their days. The greater part of parasites,
especially of fish, are introduced with the first nourishment. As soon
as they issue from the egg, young rays, like young turbots, are
already stuffed with worms which afterward obstruct the digestive
organs. The stomach of each of these fishes is like a filter which
allows every thing which is food to pass, but detains on its passage
and without any change all that is living. When we examine the stomach
and observe the food in its different degrees of digestion, we see
distinctly the worms coming out of their holes, wallowing in that
which physiologists call chyle, and choosing afterwards at their
convenience the place where they may completely develop themselves. At
the end of a few days, the fish may have swallowed an innumerable
quantity of small animals, and if each of them introduces some worms,
we can easily understand in how short a time the intestine becomes
literally filled.
There is no organ which is sheltered from the invasion of parasites:
neither the brain, the ear, the eye, the heart, the blood, the lungs,
the spinal marrow, the nerves, the muscles, or even the bones.
Cysticerci have been found in the interior of the lobes of the brain,
in the eye-ball, in the heart, and in the substance of the bones, as 93
well as in the spinal marrow. Each kind of worm has also its favourite
place, and if it has not the chance of getting there, in order to
undergo its changes, it will perish rather than emigrate to a
situation which is not peculiar to it. One kind of worm inhabits the
digestive passages, some at the entrance, others at the place of exit;
another occupies the fossæ of the nose; a third the liver, or the
kidneys.
We may even divide parasites into two great categories, according to
the organs which they choose: those which inhabit a temporary host,
almost always instal themselves in a closed organ--in the muscles, the
heart, or the lobes of the brain; those, on the contrary, which have
arrived at their destination, and which, unlike the preceding, have a
family, occupy the stomach with its dependencies, the digestive
passages, the lungs, the nasal fossæ, the kidneys, in a word, all the
organs which are in direct communication with the exterior, in order
to leave a place of issue for their progeny. The young ones are never
enclosed. Even the blood is not free from these animals, but there are
few which lodge there, except during the act of migration.
In Egypt, Dr. Bilharz observed a distome in the blood of a man
(_Distoma hoematobium_); the _Strongylus_ of the horse has been long
known, which causes serious injuries in its vessels (_Strongylus
armatus_); as also the strongylus of the dolphin and of the porpoise
(_Strongylus inflexus_), and the filaria of the dog (_Filaria
papillosa_); and some are also found in the blood of many birds, of
reptiles, batrachians, and fishes; so that there is no class of
vertebrates which escapes.
There are some which, like leeches, seek assistance from their 94
neighbours, but are content to snatch their food as they pass, and
only attach themselves for a short time to the host which they
despoil; they retain their fishing or hunting tackle, as well as their
organs of locomotion. These parasites, which never take up their
lodging on the host which nourishes them, have no sooner sucked his
blood, or devoured his flesh, than they resume their independent life.
They do not disfigure themselves, nor put on any special costume, like
those which seek a permanent abode. Gluttony is not with them the only
moving principle of existence; they do not forget what they owe to the
world, and keep up an appearance which allows them at all times to
present themselves afresh.
Parasites are scattered over every region of the globe; they choose
their place, and observe, like all living creatures, the laws of
geographical distribution. All do not inhabit the animal kingdom; some
seek for assistance in vegetable life. Many insects lay their eggs in
seeds or fruits, and their progeny, as soon as they are hatched, find
abundant nourishment in the sap or in the farina stored up for the
young plant; others pass into a state of lethargy while the seed is
dry, and recover their activity every time that they receive a little
humidity.
The female of a coleopterous insect deposits its eggs in the nut, and
in proportion as this grows, the young larva devours the kernel. When
it is brought to table, it encloses only the skin and the excretions
of the larva. A weevil establishes itself in a similar manner in
cereal plants, and, small as it is, it may produce great calamity
by multiplying in granaries. There are even worms which lodge in 95
certain of the graminaceæ, and get completely dry with the envelope
which contains them, without ceasing to live. Their life is suspended
till the day when the seed is sufficiently softened in the earth or
the water.
We have seen that each parasite has its host: we must have a
particular name to designate it. But that does not imply that if it
find not its dwelling-place it must perish. It may only live some time
at the expense of its neighbour, and thus pass for its parasite.
Naturalists are occasionally deceived. Thus, they once believed in the
passage of the Schistocephalus of the stickleback into the intestines
of certain birds which eat them, and in which they are only found
accidentally. The Ligulæ of the Cyprinidæ, found in the intestines of
the cormorant or the goosander, are not, in our opinion at least,
worms peculiar to these birds. They are strangers which must either
emigrate again or die. Acari which originally belonged to mammals and
birds, have been found living on man, causing prurigo, or even serious
maladies, and yet these parasites are not regarded as peculiar to our
species. We might cite other examples. Who has not been annoyed by the
flea, which abandons for an instant the dog, its natural host?
Among these free parasites, many do not attach themselves to a
particular species, and well deserve the title of cosmopolitan
parasites. Thus we see that the _Ascaris lumbricoides_, so common
among children, lodges also in the ox, or the horse, the ass, and the
pig. The _Distoma hepaticum_, which is a parasite peculiar to the
sheep, if we may judge by its abundance in this animal, may find its 96
way into the liver of man, or into that of the hare, the rabbit, the
horse, the squirrel, the ass, the pig, the ox, the stag, the roebuck,
and different species of antelope. It is to be remarked that all these
animals have a vegetable regimen. By drinking the water which contains
the cercaria of this species, they grow infested by this singular
lodger. The large Echinorhyncus (_E. Gigas_) has been found in the
dog, and the pig, perhaps in the phocinæ; and instances are mentioned
in which it has even migrated into man. The _Gordius aquaticus_
appears to live and develop itself in different species of insects;
and among the articulated parasites, we meet with the _Ixodes
ricinus_, commonly called the tick, on the dog, the sheep, the
roebuck, and the hedgehog; and instances are given of its presence on
man. It has been long since proved in menageries and zoological
gardens, that the _Acarus_ of the camel is able to give a cutaneous
disease to man.
As we have before said, there are many parasites which require to be
studied in order to determine the host peculiar to each of them;
although parasites sometimes lose their way, and introduce themselves
into the wrong neighbour, yet they can live there but a short time.
Instances have been known, in which the larvæ of flies have penetrated
into man accidentally by the mouth or the nostrils. Reptiles have been
known to live a certain time in the stomach. A German physiologist,
Berthold, professor at the University of Göttingen, has given an
account of all those which have been found under such circumstances,
and the number of them is considerable; he has written a memoir on the
abode of living reptiles in man.
Among other instances, this naturalist mentions the case of a boy of 97
twelve years of age, who, in 1699, after suffering acute pain, voided
from the intestines nearly one hundred and sixty four millipedes, four
scolopendræ, two living butterflies, two worm-like ants, thirty-two
brown caterpillars of different sizes, and a coleopterous insect.
These animals lived from three to twelve days. This is not all: the
same child, two months afterwards, voided four frogs, then several
toads, and twenty-one lizards, and sometimes a live serpent was seen
for a moment at the bottom of his mouth. Happily for science, we do
not see such things seriously related in books at the present day.
The size of parasites is very various: Boerhaave mentions a
bothriocephalus three hundred ells in length; at the Academy of
Copenhagen, it was reported that a solitary tape-worm (_Tænia solium_)
had been found eight hundred ells long. Female strongyli have been
seen from two decimètres to one metre in length; and _Gordii_ of two
hundred and seventy millimètres. We have found in a fish a worm which
lived rolled up like a ball, and which measured, when unrolled, more
than a mètre.
Parasites present an extraordinary variety of forms, and the
differences between the sexes in size as well as in appearance are
greater than in any other group of animals. The male of the
_Uropitrus paradoxus_, the Urubu of Brazil, has the usual form of
a round long worm, while the female resembles a ball of cotton,
without the slightest analogy with the other worms of the order. The
Lernæans also have females excessively various in size and appearance,
while the males generally resemble each other in their external 98
characters. What is not less remarkable is, that hermaphrodite worms
often unite in couples, and that only one of the two seems to perform
the function of a female, and increases in size (_Distoma Okenii,
Bilhartzia_). It even happens that the union is so complete that
the species appears formed of two individuals fastened to each other.
The Diplozoa show us a curious example of this. The gills of breams
are usually infested by these last-mentioned worms. Nothing is more
strange than to see all these individuals united two and two as if
soldered together, each preserving its mouth and digestive canal, and
producing eggs which give birth to isolated individuals. We sometimes
see males so completely absorbed in their females, even in an
anatomical point of view, that they only represent a fragmentary
apparatus. The male of the _Syngami_ is so obliterated, that when
compared with the other males of its order it is only a testicle
living on the female.
Should an organ infested with worms be considered diseased, simply on
account of their presence? We hesitate not to say that, as long as
these guests cause no disorders, there is no pathological condition.
The child which has _Ascarides lumbricoides_ in its stomach is
not necessarily ill. All animals in a wild state always have their
parasites; they lose them rapidly when in captivity.
The Abyssinians do not take medicine when they have tæniæ; on the
contrary they are in a better state of health. Do we not find medical
men prescr
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