Whatever may be the modes of procedure employed by the star-fish, it is now clearly ascertained, however incredible the fact may at first appear, that it swallows oysters in the same manner as is practised at the oyster-shop.
This little being, formed of five arms and without any other apparent member, accomplishes a work which man is quite unable to execute—it opens an oyster without an oyster-knife.
If reasoning man had no other means of nourishment than oysters, and was without a knife to open them, it is very certain that with all his genius he would be puzzled how to get at the inaccessible and savoury bivalve so obstinately closed against him. The star-fish devours dead flesh of all kinds; their sole occupation is to feed themselves, and they keep up an incessant and active chase after all sorts of corrupt animal matter. The Asterias thus perform in the bosom of the sea the same part that certain birds and insects play on shore; they are its scavengers, and feed their bodies upon the carcases of animals which, if abandoned to the action of the elements, would become a cause of infection.
In the same manner that certain animals render the air healthy, the Asterias help, on a considerable scale, to keep the sea which shelters them in a pure and healthy state. Zoologists are not agreed upon the manner in which respiration operates on the star-fishes. Nevertheless they think that the principal part in this phenomenon devolves upon the subcutaneous branchiæ which in each ray constitute two double series of bladders. The function of circulation is equally unknown. The vascular apparatus is sufficiently developed in this zoophyte, and appears to have for its centre an elongated canal with muscular walls, which may with justice be honoured with the name of heart. A little ring surrounding the œsophagus, and from which issue certain delicate white chords, which are prolonged into the furrows of the arms, presents us with all that can be designated a nervous system in the star-fishes. Among organs of sense we may mention, as the apparatus of touch, the tentacular ambulacra, as well as those which are disseminated upon the dorsal surface of the disk. The eyes are considered to be certain bright red points which are situated at the extremity of the arms and on the under surface—a most singular position for the organs of sight. The eyes must, besides, be very imperfect, for they possess no crystalline lens. Ehrenberg insists upon the existence of eyes in some species, attributing the function to those red spots, however; while Rymer Jones attributes the indications in which this originates to an extremely delicate sense of touch in the star-fishes. Professor Edward Forbes, while he admits the existence of ganglions in the nervous system to be extremely doubtful, seems, by the frequent use of the terms eye and eyelids, to admit that the specks in question are visual organs; the weight of authority inclines therefore to Ehrenberg's view, that if not eyes in the strict sense of the term, they serve the purposes of vision, modified and adapted to the wants of the animal.
The star-fishes have distinct sexes, with individual differences; their eggs, which are round and reddish, undergo curious phases of development. They produce little worm-like creatures, covered with vibratile hairs, like the infusoria, which swim about with great vivacity; these little creatures are subject to considerable changes. In the year 1835 M. Sars described, under the name of Bipinnaria asterigera, an enigmatical animal resembling a polyp from the arms at one extremity of the body, while the other terminated in a tail, furnished with two fins; but it was chiefly remarkable as having an Asterias attached to the extremity which carried the arm. He expressed an opinion, which was soon placed beyond any doubt, that this bipinnaria was an Asterias in its course of development. The egg becomes a sort of infusoria, the infusoria becomes a bipinnaria, and this produces the Asterias. In short, the Bipinnaria does not become an Asterias by any metamorphoses analogous to that so well known amongst insects—the butterfly, for example—but becomes, so to speak, the foster-mother or nurse to the Bipinnaria. The larva is large, and it is at the cost of a very small internal rudiment of this larva that the Asterias is developed: the Asterias robs the larva of its stomach and intestines, and turns it into a visceral apparatus for its own use. But the Asterias makes itself a mouth of any of the pieces most remote from the primitive mouth of the larva. Thus the Bipinnaria divides itself; it gives its stomach and intestines, and keeps its œsophagus and mouth, and it can live several days after the Asterias is detached from it.
Can any one imagine the existence of a being with only a mouth and œsophagus, which has neither stomach nor intestines, because another animal has possessed itself of them for its own use? The study of the lower animals abounds in surprises of this kind. It is a chain of unforeseen facts; of natural impossibilities; of realized points necessarily reversing all notions obtained in the study of beings which have a higher place in the animal scale. The history of the star-fishes would be incomplete were we to omit mentioning the most remarkable traits of their organisation with which naturalists are acquainted. The animals exhibit in the highest degree the vital phenomena of dismemberment and restoration, that is to say, of the faculty of reconstructing organs which they have lost. These arms, the structure of which is so complicated, and which protect such important organs, may be destroyed by accident. The animal troubles itself little at this mutilation: if he loses an arm it disquiets him but little; another is immediately procured. We often see in our collections of Asterias specimens wanting in symmetry because they have been taken before the new members which are in process of development have attained their definite length. Professor Rymer Jones mentions an instance of redintegration very complete and most curious. This naturalist had an isolated ray of Asterias which he had picked up; at the end of five days he observed that four little rays and a mouth had been produced; at the end of a month the old ray was completely destroyed, and this apparently useless fragment had been replaced by a new being, quite perfect, with four little symmetrical branches. This faculty of reproducing organs, which we have noted in describing the fresh water polyps, the sea anemone, &c., exists also in many other zoophytes, but in none more strikingly than in the Asterias. But a still more startling fact remains to be mentioned: one more strange and more mysterious, for it does not belong to the physical or organic order, but appears to belong to the moral world. The star-fishes commit suicide! Certain of these animals appear to escape from dangers which menace them by self-destruction. This power of putting an end to existence we only find on the highest and lowest steps of the animal scale. Man and the star-fishes have a common moral platform, and it is that of self-destruction! This power of dismemberment, however, seems to be confined to the Ophiocoma and Luidia—at least, it is only carried out to its full extent in these generæ.
Mysteries of Nature, who can sound your depths? Secrets of the moral world, what being but God has the privilege of comprehending you? A large species of Star-fish (Luidia fragillissima), which inhabits the English seas, has this instinct of suicide to a great extent. The following account by Professor Edward Forbes of an attempt to capture a Luidia gives a good illustration of its powers. "The first time that I took one of these creatures," the professor says, "I succeeded in placing it entire in my boat. Not having seen one before, and being ignorant of its suicidal powers, I spread it out on a rowing bench, the better to admire its form and colours. On attempting to remove it for preservation, to my horror and disappointment I found only an assemblage of detached members. My conservative endeavours were all neutralised by its destructive exertions; and the animal is now badly represented in my cabinet by a diskless arm and an armless disk. Next time I went to dredge at the same spot I determined not to be cheated out of my specimen a second time. I carried with me a bucket of fresh water, for which the star-fishes evince a great antipathy. As I hoped, a Luidia soon came up in the dredge—a most gorgeous specimen. As the animal does not generally break up until it is raised to the surface of the sea, I carefully and anxiously plunged my bucket to a level with the dredge's mouth, and softly introduced the Luidia into the fresh water. Whether the cold was too much for it, or the sight of the bucket was too terrific, I do not know; but in a moment it began to dissolve its corporation, and I saw its limbs escaping through every mesh of the dredge. In my despair I seized the largest piece, and brought up the extremity of an arm with its terminal eye, the spinous eyelid of which opened and closed with something exceedingly like a wink of derision."
The mind remains confounded before such spectacles, and we can only say, with Mallebranche, "It is well to comprehend clearly that there are some things which are absolutely incomprehensible."