them.* When Bohadsch saw this structure for the first time it seemed to him so anomalous and wonderful, that numerous dissections were required to convince him of its being the natural armature of the organ, and he fell into the erroneous conclusion that it was fitted to triturate the shells on which the animal was presumed to prey. † But the Aplysia is really herbivorous, as is asserted by Pessonel, Cuvier, and others; and, were it necessary, I could add my testimony to this fact, having at one time kept a large specimen of Aplysia mustelina for nearly three months in a state of confinement, during which it was fed on fuci only, and these it ate greedily, showing some partiality to the Dulse (Fucus palmatus). The food, previously to its reception in this curious gizzard, has passed through a large membranous crop, in which it probably undergoes little change in the gizzard it is broken down, and in this state enters a third stomach, armed also on its internal surface with hook-like prickles directed forwards, and intended, doubtless, to tease the fibrous mass, that it may be more thoroughly subjected to the dissolving virtue of the gastric juices, and reduced to a homogeneous pulp previously to its commixture with the bile, which flows into this viscus from two large orifices close to the pylorus, opening between two small membranous prominent crests. § Among the other families of Gasteropods, I do not remember any that are exclusively carnivorous, except the genus Testacellus, to outward appearance scarcely differing from the common slug, but distinguished by carrying a small shell above the tail; and a species of Vitrina, or shelled terrestrial snail, found under stones in moist, shady, or grassy situations in the higher parts of the Island of Madeira. Unlike the slugs, the Testacellus burrows in the soil, and is the dread of the earthworm on which it feeds; and these habits are accompanied with corresponding changes in its organisation. Its body is more cylindrical than that of the * Pessonel's description of this organ is short, but characteristic:-" The membranes are thick, and are set with twelve stones, or horny pieces, of a bright yellow colour, and as transparent as fine yellow amber, ending in points like a diamond; so that the great side, or basis, is set into the membrane of the gizzard, as a diamond in its socket. Others differ in size, having different figures, that, in acting all together, they may be able to break and grind the herbs the animal feeds upon, as well by the strength of the muscle, or gizzard, which puts them into action, as by the situation of these stones, assisted by grains of sand found in it, turning the whole by this trituration into a liquor." Phil. Trans. vol. 50, 1758, p. 587. Darwin's Journal, iii. 6. + De Anim. Mar., p. 19 and 22. § Cuv. Mollusq. Mem. ix. 18. slug, and, in lieu of a shield confined to a limited portion of the neck, the whole body is encased with a thick coriaceous coat, to guard from the additional pressure to which it is exposed, and to afford sufficient strength to execute its furrows. But the most marked differences are found in the digestive organs. In the mouth there is no corneous denticulated jaw, nor a membranous spinigerous tongue; but from between two vertical lips issues a very small cylindrical proboscis, and appropriated to it a muscle which forms the most curious part in the structure of the creature. It is large, cylindrical, lies along the whole belly, and is attached to the left side of the back by a dozen of very distinct fleshy slips, almost perpendicular to the principal muscle of the body.* The size and strength of this muscle indicate its paramount importance; and its actions are of a twofold nature. When the Testacellus has become aware of the presence of a prey, to surprise and take it unawares is necessary, for the earthworm when alarmed is more alert by far than its foe. The advantage is given to the latter by having the power, through the medium of this muscle, of suddenly darting out the proboscis, which in an instant is projected and applied to the object in view. It is then retracted by the same muscular apparatus, and made simultaneously to grasp with firmness the struggling victims of its ferocity. Mr. G. B. Sowerby, in reference to Testacellus scutulum, says he was surprised "that an animal generally so extremely sluggish in its motions, after discovering its prey by means of its tentacula, thrusting from its large mouth its white, crenulated, revolute tongue, should instantly seize upon, with extraordinary rapidity, and firmly retain, an earthworm of much greater size and apparent force than itself; but which, by its utmost exertion, is unable to escape." To increase its power of retaining a secure hold, the tongue is furnished, around and just beneath (if not upon) its margin, on the outside, with short hair-like bristles.† The carnivorous Vitrina (Helicolimax lamarckii of Fe-· russac) differs from our native species in some respects; but, according to the Rev. Mr. Lowe, to whom we owe our acquaintance with its habits, "is so closely allied, that it would be very rash at present to separate it" from the genus. When leaves and other vegetable matters were * Cuv. Mem. xii. 7. + Mag. Nat. Hist. vii. 227 and 414. This opinion of Mr. Lowe's is confirmed by the anatomy of the species, excellently developed by the Rev. M. J. Berkeley, Zool. Journ. No. xix. p. 305. given to it, they were never touched, even although care was taken that the Vitrina should have nothing else for nearly a fortnight; but, on the very first night of its confinement, it would kill and eat a small snail, and it preyed on its own species greedily, the larger slaying the smaller, and then indulging its cannibal appetite. Two of nearly equal size being put together, the stronger or braver slew his neighbour, which furnished a plentiful repast for two or three succeeding nights, for it is during this season only that they feed.* It would be well to ascertain whether our own Vitrinæ are not equally carnivorous and addicted to cannibalism: they are at present believed to be herbivorous; but Mr. Jeffreys informs us that V. pellucida " has the same carnivorous propensities as the smaller Limacidæ and Testacelli; and I once," he adds, "detected no less than seven individuals busily engaged in feeding on a scarcely dead earthworm, which was faintly writhing about, and endeavouring in vain to get rid of its assailants."+ The Pteropod Mollusca are undoubtedly zoophagous; the minute Crustacea and Medusa, or particles of dead animal matter floating in the sea, furnishing their nutriment Some species of this order abound amazingly in the Arctic Ocean, where the marine vegetation seems too scanty for the requisite supply of food; and, moreover, they are found floating far from the shore, and at the surface, where no vegetables are. We have, however, no certain information on this head. On the contrary, it is well ascertained that all the Cephalopoda are carnivorous, and for voraciousness and ferocity may justly claim precedence among mollusks. Such of them as swim in the bosom of the ocean, as Loligo, feed upon fish in general, and they will frequently tear large pieces from those which have swallowed the baited hook, and deprive the fisherman of his gain. I have had more than one specimen of Loligo vulgaris brought me, which, adhering with a fatal tenacity to the fish, had allowed itself to be drawn from the water; and in the stomachs of others I have found not only the undigested remains of this food, but the beaks of small individuals of their own species. The tribes, again (Octo * Lowe in Zool. Journ. iv. 342. + Linn. Trans. xvi. 506. The fact of their feeding on their own kind was known to Elian, who thus speaks of the Polypus in the first chapter of his Miscellanies :-"They have terrible stomachs, and nothing can save itself from being devoured by them. They frequently attack one another, when the smaller one, being caught and involved in the tresses of the more powerful, becomes a meal for it." podeæ and Nautili,)* whose habit is to crawl along the bottom, and seek concealment in rocky places, prey principally on the larger Crustacea, which find in their hard spiny shells, and their powerful claws, no protection against these voracious enemies. In the Mediterranean, the Octopi are held in detestation by the fishermen, because of the havoc they commit among the most esteemed species of lobsters and crabs, which is so extensive that scarcely any are to be found in their usual haunts during the summer season, and what have chanced to escape evince, by their mutilated condition, the peril they have run.† According to the early naturalists, the cuttle entraps its prey, partly, at least, by stratagem: "And albeit otherwise it be a very brutish and senselesse creature, so foolish withall, that it will swim and come to a man's hand; yet it seems after a sort to be witty and wise, keeping of house and maintaining a familie: for all that they can take they carry home to their nest. When they have eaten the meat of the fishes, they throw the empty shels out of dores, and lie as it were in ambuscado behind, to watch and catch fishes that swimme thither." Pliny also informs us, on the authority of Trebius Niger, that the Cephalopoda "Are most desirous and greedie of cockles, muscles, and such like shell fishes;" and in order to reach the animal scatheless, they "lie in wait to spie when the said cockles, &c., gape wide open, and put in a little stone between the shels, but yet beside the flesh and bodie of the fish, for feare lest, if it touched and felt it, she would cast it forth again: thus they theeve, and without all danger, and in securitie get out the fleshie substance of the meat to devoure it: the poor cockles draw their shels together for to clasp them between (as is above said), but all in vaine, for by reason of a wedge between, they will not meet close, nor come neere together. See how subtle and craftie in this point these creatures be, which otherwise are most sottish and senseless."§ + The cuttlefish, I need scarcely remark, are all guiltless of this clever stratagem: their warfare, though cruel, is open, and they are amply furnished with the necessary weapons. The long flexible arms which encircle the head are set along their inner aspects, with numerous cup-like suckers, which the animal can fix to any object, and the adhesion is strengthened by a horny ring round the edge of each sucker often pointed with sharp curved teeth. (Fig. 60. a.) + Cuvier, Mem. i. 4. § Holland's Pliny, i. 251. * Owen's Mem. on the Pearly Nautilus, 24. Holland's Pliny, i. 250. Fig. 60. "When an animal of this kind approaches any body with its suckers, in order to apply them more intimately, it presents them in a flat or plain state; and when the suckers are thus fixed by the harmony of surfaces, the animal contracts the sphincter, and forms a cavity in the centre, which becomes a vacuum. By this contrivance, the sucker adheres to the surface with a force proportioned to its area, and the weight of the column of air and water, of which it constitutes the base. This force, multiplied by the number of suckers, gives that by which all or a part of the feet adhere to any body. This power of adhesion is such, that it is easier to tear off the feet than to separate them from the substance to which the animal chooses to attach itself." It must, then, be a fearful thing, for any living creature, to come within their compass, or within their leap, for captured by a sudden spring of several feet, made "with the rapidity of lightning," and entangled in the slimy serpentine grasp of eight or ten arms, and held by the pressure of some hundreds of exhausted cups, escape is hopeless, and the struggles of the hapless victim, by bringing its body into more rapid contact with the suckers not yet applied, only accelerate its fate. The jaws, and a portion of the enlarged part of the foot, of Loligo sagittata. of 66 As a sort of illustration I may remind you of the following fishing custom of the natives of the South Sea Islands: They have a curious contrivance for taking several kinds ray and cuttle-fish, which resort to the holes of the coral rocks, and protrude their arms or feet for the bait, but remain themselves firm within the retreat. The instrument employed consists of a straight piece of hard wood, a foot long, round, and polished, and not half-an-inch in diameter. Near one end of this, a number of the most beautiful pieces of the cowrie or tiger-shell are fastened one over another, like the scales of a fish or the plates of a piece of armour, until it is about the size of a turkey's egg, and resembles the cowrie. It is suspended in an horizontal position by a strong line, and lowered by the fisherman from a small canoe, Cuvier, Comp. Anat. Trans. i. 432. See also Roget, Bridgew. Treat. i. 260. |