mediate between the Zoophagan Trachelipods and the Cephalopods. They have four swimming organs. There seems a considerable affinity between this tribe and the Pteropods in these organs, which indicates a circular arrangement in the univalve Molluscans. The Carinaria vitrea is one of the rarest shells that is known, arising probably from its extremely fragile conch, which is nearly as transparent as glass. A model of it in wax may be seen in the British Museum. The animal is a sailor like the Argonaut, to which it comes near. It is found in the South Seas. There are two other species known, one of which frequents the Mediterranean. Some genera without shells are placed in this order by Lamarck. They swim horizontally like fishes, which circumstance, in conjunction with their fins or swimming organs, induced him to place them at the end of the Molluscans as near the fishes; several authors consider them as belonging to the Pteropods, to which they are certainly related. 303 CHAPTER X. Functions and Instincts. Cephalopods. We have now taken leave of what may be called the proper Molluscans, including the Bivalves, and Univalves1 of Aristotle and Linné, or the Conchifers and Molluscans of Lamarck, and are arrived at a Class remarkable, not only for their organization, form and habits, but also for their position in the animal kingdom; for in their composition they seem to include elements from both the great divisions of that kingdom: from the Vertebrates-the beak, the eye, the tongue, an organ for hearing, the crop, the gizzard, and an analogue of the spine, with several other parts enumerated by Cuvier; and from their own sub-kingdom, many of their remaining organs. We may descend to the very basis of the animal kingdom for the first draught of their nervous system, for it is discoverable in the wheel-animals in which Ehrenberg detected pharyngal ganglions and a nuchal nervous collar; the sucker 1 Διθυρα. Μονοθυρα. 2 Ganglia nervea pharyngea. Annulus nerveus nuchalis. Ehren. bearing arms seem to have their first outline in the fresh water polypes;' indeed if the mouth of the cuttle-fish with its suckers, be separated from the head, leaving behind the long arms, we see immediately an analogue of a radiary, particularly of a star-fish, with its rays bearing suckers below, and its central mouth. The lamellated tentacles observed by Mr. Owen in his work, before quoted, on the animal of the Pearly Nautilus, above and below the eyes, seem to lead to the antennæ of Crustaceans and Insects, and numerous Molluscan characters are obvious to every one. From these circumstances it seems evident that the Creator has placed this tribe in a station which leads to very different and distant points in the animal kingdom, and that there is scarcely any but what may recognize in it one or more of its own peculiar features-yet at the same time it exhibits many characters, both in its most extraordinary outward form and in its internal organization, that are quite peculiar and sui generis, of which no animal at present known exhibits the slightest traces. To mention only its muscular apparatus adapted to its unparalleled form; its system of circulation, carried on in the first Order by three distinct organs instead of one heart; and the wonderful complication of their tentacles, of 1 Hydra. 2 Nautilus Pompilius. the nerves that move them, and the vascular system that animates them. pre This singular Class, which Cuvier denominated Cephalopods, or having their feet attached to their head, appears to follow very naturally the Trachelipods and Heteropods, lately described, which have not only eyes furnished with iris and pupil, but also distinct sexes, and are of daceous habits, all characters which they possess in common with the Cephalopods or Cuttle-fish. There is, however, an animal amongst the naked Gastropods-called by the ancients, from its tentacles representing the ears of a hare, the seahare,' a name it still bears in Italy, which Linné named Laplysia, in which he was followed by Lamarck, but modern writers after Gmelin have called it Aplysia, a name used by Aristotle for a very different animal, a kind of sponge,' and, therefore, improperly applied-this animal has many characters that are found in some of the Cephalopods, particularly in its circulating and nervous systems; in having internal solid parts, and in discolouring the water with an inky fluid, so that there seems also a connection between this genus and the Cephalopods amounting to something more than a mere analogical resemblance. Mr. Owen has divided this Class into two 1 Lepus marinus, Plin. VOL. I. 2 Hist. An. 1. v. c. 16. X Orders, from the composition of their respiratory organs, namely, those that have two branchiæ,' or gills, and those that have four. The first includes those that have no shell, and the second those that have one. The last is further divisible into those whose shell has many chambers, as the Nautilus, and those where it has only one, as the Argonaut, or paper nautilus. To the first of these Orders belongs the cuttlefish, one of the most wonderful works of the Creator. Its mouth is surrounded by eight long fleshy arms, or rather legs, somewhat conical in shape, and acute at the end, moved by innumerable nerves, furnished from numerous ganglions these legs can bend in every direction with the utmost vigour and activity, their surface is furnished with many suckers, by which they can fix themselves strongly to any thing they wish to lay hold of, and by means of which, like the star-fish, they can move from place to place. When this animal walks, in this resembling also the star-fish and sea-urchin,3 it moves with its head and mouth downwards and its body elevated. It swims also and seizes its prey by means of these organs: besides these arms or legs, for they perform the functions of both, there is a pair of long organs, one on 1 Dibranchiata. 3 Sepia. 5 Ibid, p. 212. 2 Tetrabranchiata. |