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.