This is doubtless the reason that in collections of natural history we rarely find star-fishes, and especially the Luidia, entire; the moment the animal is seized by fisherman or amateur, in its terror or despair it breaks itself up into small fragments. To preserve them whole they must be killed suddenly, before they have time to be aware of their danger. For this purpose, the moment they are drawn from the sea they must be plunged into a vase of cold fresh water; this saltless liquid is instant death to these creatures, which in this condition perish suddenly before they have time to mutilate themselves. The star-fish is a curious ornament in our natural history collections, but in this state they represent very imperfectly the elegance and particular grace of this curious type. To understand the star-fishes, they must be seen in an aquarium, where we can admire the form, figure, movements, and manners of these marvellous beings.
The Asterias are the planets of the sea. It may be said that heaven, reflected during the night on the silvery surface of the ocean, let fall some of those stars into its depths which decorate the resplendent vault.
Crinoïdea.
We quoted the maxim of Linnæus in the earlier pages of this volume, that Nature makes no leaps. Nature proceeds by means of insensible transitions, rising by degrees from one organic form to another. Most of the animals hitherto described are immovably fixed to some solid object; at least, such is their condition in the adult state. We are about to describe zoophytes free of all fetters; animals "which walk in their strength and liberty."
Between zoophytes fixed to the soil, like the corals, gorgons, and aggregate zoophytes, such as sea-urchins and holothurias, Nature has placed an intermediate race, namely, the Crinoïdea, a class of zoophytes which are attached to a rock by a sort of root armed with claws, having a long flexible stem, which enables them to execute movements in the circle limited only by the length of this stem, just as the ox or goat in our paddocks is confined by its tether to the space circumscribed by the length of its rope.
Let the reader picture to himself a star-fish borne upon the summit of a flexible stem firmly rooted in the soil, and he has a general idea of the zoophytes which compose the order of the Crinoïdea. Naturalists of the seventeenth century bestowed the name of stone lilies on these curious products. This rather poetical name proves that the conformation of these creatures had at an early period attracted observation, presenting the naturalist with the most curious of his lessons. The encrinites raise, as from the dead, a whole world buried in the abyss of the past. At the present time only two genera of these zoophytes exist, whilst in the early ages of the world the ocean must have swarmed with them. Encrinites abounded in the seas during the transition and secondary epoch. It was one of the most numerous of the animal tribes which inhabited the salt waters of the ancient world. In traversing some parts of France, we tread under our feet myriads of these beings, whose calcareous remains form vast beds of rock. The encrinites gradually disappeared from the ancient seas; their species were diminished as the globe became older or modified in its conditions, so that at the present time only a few types remain in our seas—such as the Comatula of the Mediterranean; Pentacrinus, the Medusa's-head of the Antilles; and the European Pentacrinus—all of them very rare, and probably destined soon to disappear, carrying with them the last reminiscence of the zoological races of the ancient world: and here lies the real interest which the Crinoïdea presents to the thinking man. The encrinites most common in the fossil state are Pentacrinus fasciculosus, belonging to the lias; Apiocrinus rotundus, which is found in the oolite or jurassic rocks; and Encrinus liliformis, which appertains to the Triassic period. These three fixed zoophytes seem to have existed in great numbers during an early age of the world—namely, the Silurian period. They attained their maximum of development during the Devonian age, after which they begin to decrease. According to M. D'Orbigny, there are thirty-nine genera found in the palæozoic rocks, two in the triassic, seven in the jurassic, five in the cretaceous, and only one in the tertiary strata. Of all these genera only one, namely, Pentacrinus, is found in the modern epoch to represent the varied forms of these the first inhabitants of the seas.
The free Crinoïdæ, that is, those not rooted to the soil by a stem, of which the Comatula may be considered the type, only appeared at a later period. They are absent in the palæozoic and triassic rocks, but appear to have attained their maximum of development in the jurassic period.
The numerous fossilized remains of these curious creations, which abound in different rocks, attracted the attention of learned men at an early period. The encrinites were among the earliest objects of scientific description. As early as the sixteenth century, the celebrated mineralogist, George Agricola, mentions them under the names of Entrochites, Trochites, and Astroïtes. At the same time, and since that epoch, the Crinoïdæ, which we know by the name of stone-lilies, and which characterises the Muschelkalk rocks, have been known under the name of Encrinus, from εν, stone, and κρίνον, a lily.
Fig. 107. Pentacrinus caput Medusæ (Müller).