THE INTERNATIONAL SCIENTIFIC SERIES.
VOLUME XIX.
THE INTERNATIONAL SCIENTIFIC SERIES.
_Works already Published._
I. FORMS OF WATER, IN CLOUDS, RAIN, RIVERS, ICE, AND GLACIERS.
By Prof. JOHN TYNDALL, LL. D., F. R. S. 1 vol. Cloth.
Price, $1.50.
II. PHYSICS AND POLITICS; OR, THOUGHTS ON THE APPLICATION OF THE
PRINCIPLES OF "NATURAL SELECTION" AND "INHERITANCE" TO
POLITICAL SOCIETY. By WALTER BAGEHOT, Esq., author of "The
English Constitution," 1 vol. Cloth. Price, $1.50.
III. FOODS. By EDWARD SMITH, M. D., LL. B., F. R. S. 1 vol.
Cloth. Price, $1.75.
IV. MIND AND BODY: THE THEORIES OF THEIR RELATIONS. By ALEX.
BAIN, LL. D., Professor of Logic in the University of
Aberdeen. 1 vol., 12mo. Cloth. Price, $1.50.
V. THE STUDY OF SOCIOLOGY. By HERBERT SPENCER. Price, $1.50.
VI. THE NEW CHEMISTRY. By Prof. JOSIAH P. COOKE, Jr., of Harvard
University. 1 vol., 12mo. Cloth. Price, $2.00.
VII. THE CONSERVATION OF ENERGY. By Prof. BALFOUR STEWART, LL. D.,
F. R. S. 1 vol., 12mo. Cloth. Price, $1.50.
VIII. ANIMAL LOCOMOTION; OR, WALKING, SWIMMING, AND FLYING, WITH A
DISSERTATION ON AËRONAUTICS. By J. BELL PETTIGREW, M. D.,
F. R. S. E., F. R. C. P. E. 1 vol., 12mo. Fully
illustrated. Price, $1.75.
IX. RESPONSIBILITY IN MENTAL DISEASE. By HENRY MAUDSLEY, M. D.
1 vol., 12mo. Cloth. Price, $1.50.
X. THE SCIENCE OF LAW. By Prof. SHELDON AMOS. 1 vol., 12mo.
Cloth. Price, $1.75.
XI. ANIMAL MECHANISM. A TREATISE ON TERRESTRIAL AND AËRIAL
LOCOMOTION. By E. J. MAREY. With 117 Illustrations.
Price, $1.75.
XII. THE HISTORY OF THE CONFLICT BETWEEN RELIGION AND SCIENCE. By
JOHN WM. DRAPER, M. D., LL. D., author of "The Intellectual
Development of Europe." Price, $1.75.
XIII. THE DOCTRINE OF DESCENT, AND DARWINISM. By Prof. OSCAR
SCHMIDT, Strasburg University. Price, $1.50.
XIV. THE CHEMISTRY OF LIGHT AND PHOTOGRAPHY. IN ITS APPLICATION TO
ART, SCIENCE, AND INDUSTRY. By Dr. HERMANN VOGEL. 100
Illustrations. Price, $2.00.
XV. FUNGI; THEIR NATURE, INFLUENCE, AND USES. By M. C. COOKE, M.
A., LL. D. Edited by Rev. M. J. BERKELEY, M. A., F. L. S.
With 109 Illustrations. Price, $1.50.
XVI. THE LIFE AND GROWTH OF LANGUAGE. By Prof. W. D. WHITNEY,
of Yale College. Price, $1.50.
XVII. MONEY AND THE MECHANISM OF EXCHANGE. By W. STANLEY
JEVONS, M. A., F. R. S., Professor of Logic and Political
Economy in the Owens College, Manchester. Price, $1.75.
XVIII. THE NATURE OF LIGHT, WITH A GENERAL ACCOUNT OF PHYSICAL
OPTICS. By Dr. EUGENE LOMMEL, Professor of Physics in the
University of Erlangen. With 188 Illustrations and a Plate
of Spectra in Chromolithography. Price, $2.00.
XIX. ANIMAL PARASITES AND MESSMATES. By Monsieur VAN BENEDEN,
Professor of the University of Louvain, Correspondent of
the Institute of France. With 83 Illustrations.
(_In press._)
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,
549 & 551 BROADWAY.
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.