hepatic ducts are obviously continuations developed from the stomach itself, and the obliquity of their entrance does not protect them from the ingress of the food. We observe opening, also, into the stomach of the Doris, which is destitute of teeth, a glandular cœcum of a pyriform shape. That glandular cœcum differs obviously in its structure and form from the structure of the liver. It consists of a single wide cavity, studded internally with minute glandular orifices or follicles: it opens into the pyloric extremity of the stomach, and, consequently, pours its secretion into the alimentary canal at the same place with the liver. From this position of the organ, and this termination of its duct, we cannot consider it as analogous to the salivary glands. From its position in the vicinity of the hepatic organ, it is rather analogous to the pancreas in higher animals. This I was more anxious to examine, on account of its having been stated by Cuvier and by many other writers, that no invertebrated animals possess a pancreas. Tiedemann has adopted my view of this gland; Meckel, in his last work, was inclined to do the same; but Cuvier continued to regard it as a peculiar organ. This form of the pancreas exists also in the Aplysia and some other Gasteropods; and I have also shown that, under a more complicated form, that organ exists in the Cephalopods."*

It has often been remarked that the liver of the mollusca is proportionably more voluminous than in other animals, and of a looser texture. In many of them it is deeply lobulated, so much so in the genus Onchidium that it seems to have three livers, and in some Tritoniæ it is broken up into branched lobes, which are prolonged into the branchial plumes garnishing the sides of the body. And this approach towards disintegration reaches its acme in the Eolidæ, where the biliary furnisher becomes a mere lining to a set of vessels connected with the alimentary canal, and to which Milne-Edwards has applied the term 'gastro-vascular." The name was intended to indicate to us that in these vessels there was a combination of the functions of the digestive and circulating organs-organs of chylification as well as of assimilation; and although doubts may exist relative to their fitness for this double duty, yet the name may be retained as pointing out the vascular-like character of these intestinal appendages.

*The Lancet, No. 572, p. 708-9, and Edin. Phil. Journ. xiii. p. 198. + Lister Exer. Anat. de Coch. terr. p. 79, 80.

The system is found fully developed only in the Eolidæ. In these delicate and beautiful Nudibranches the short œsophagus leads into a comparatively large pear-shaped stomach; and from the upper surface of its posterior extremity a short intestine proceeds, which, after a slightly tortuous course, terminates anteriorly, on the right side of the body, in a small nipple-like vent. But, besides this intestine, another chylous vessel is continued from the stomach, in the form of a wide tapering canal, along the median line, and terminates near the posterior extremity of the body in a blind sac. From the stomach itself, as well as from its continuation, branches are given off in pairs, not, however, in perfect symmetrical order, but always more or less alternating. These branches give off smaller tubes, which are continued into the branchial papillæ, and lined with a follicular apparatus for the biliary secretion. The enclosed figures (Fig. 67), copied from the engravings of

Fig. 67.

Messrs. Hancock and Embleton, will give you a correct idea of what I have attempted too shortly to describe;*

On the Anatomy of Eolis, in Ann. and Mag. N. Hist. xv. p. i., and 77. See also Ann. and Mag. N. Hist. xii. 236; and Allman on the Anatomy of Actæon, in vol. xvi. 146.

but you must remember that the dendritic character of the system is not always so much exaggerated, if I may use the expression. It varies, in fact, considerably in the different genera, passing through some intermediate steps to its full developement, and again receding to normal simplicity in other genera, as in Limapontia and Chalides, in whom there are only two large pouches for the retention and elaboration of the alimentary matters.*

Now, you must beware of believing in the existence of any unbroken barrier between the mollusca that feed on herbage and the mollusca that feed on flesh. That certain families are herbaceous and others carnivorous, under ordinary circumstances, is very true; but in every order or class you will find some genera or species that break the rule, and indulge in a diet repulsive to the class as a body. Perhaps no mollusks are so pre-eminently carnivorous as the Cephalopods, but I know that some of them do feed occasionally,-not on olives, as Pliny tells us,† but on sea-weed, for I have found the stomach of Loligo sagittata crammed full of fragments of the midrib of Alaria esculenta, and pieces of the same were sticking between the mandibles, as if the creature had been killed in the act of eating. The Scalaria, Turritella, Velutina, Ianthina, and Stylifer, genera which the characters of their shells would decide to be herbivorous, are really and exclusively carnivorous. The favourite food of the Ianthina appears to be the gelatinous Velella, whence, it is said, that it derives the blue tincture of its shell; and the Stilifer lives a parasite amid the forest of spines that clothes the Echinus, or burrows under the skin of the star-fish, upon whose juices there is reason to believe that it feeds. "With that instinct of self-preservation imparted to all parasites whose existence depends upon that of their nidus, the Stilifer, like the Ichneumon among insects, appears to avoid the vital parts; for in no instance did Mr. Cuming find it imbedded anywhere save in the rays, though some had penetrated at their base and very near the pelvis."

Of the Nudibranches, which are usually, and, with regard to many of them, properly classified with phytivorous mollusks, the greater number appear to be animal feeders.

* Ann. des Sc. Nat. (1844) i. 16. Also the vol. for 1845, p. 275.

+ Of the Octopodus, Rondeletius says,-"Ils mangent les coquilles de mer, ils aiment fort les branches de l'olivier, et par cette friandise on les prend, ils aiment aussi le figuier.”—Hist. des Pois. i. 373.

Broderip in Proc. Zool. Soc. ii. 60.

*

This must of necessity be the case with those which swim in the open sea, and with those which live amidst the plant-like corallines and florulent zoophytes, embracing the majority of the Tritoniada and Eolida; for, at the depths in which these animated productions are found, no sea-weeds can grow. Thus Mr. Bennet tells us that the Glaucus feeds greedily on the gelatinous Porpitæ and Velellæ ;† and in the fleshy gizzard of the toothless and tongueless Tethys, Cuvier found fragments of shells, and the legs and other remains of little crabs. I took what appeared to be the fry (Fig. 68) of Asterias papposa from the stomach of a Tritonia; and Sir John Graham Dalyell assures us that the appropriate food of Tritonia hombergii is the Lobularia digitata, a common and nauseous zoophyte.§ Messrs. Alder and Hancock have seen the Eolis punctata devour other Nudibranches, and make a repast of its own spawn; and Eolis coronata, with equal carnivorous propensities, does not hesitate to feed on its own species, the weaker falling Fig. 68.

a sacrifice to the cravings of the stronger. "Large individuals will content themselves with plucking off each other's papillæ; but, should a smaller specimen be within reach, it is most mercilessly attacked, the more powerful animal laying hold of any part of the weaker that may happen to be nearest. The tail, however, is generally first seized, and fierce and determined is the onset. The de

* Many testaceous Gasteropods, which we conclude to be herbivorous from the character of the shell, live at depths where sea-weeds are very rare or awanting. These species may be presumed to live on corallines. "Now that the observations of M. Decaisne, M. Kutzing and others have so clearly proved the vegetable nature of that singular production (the Nullipore), so long regarded as a zoophyte, the source of the food of the holostomatous testacea in these deep regions is no longer problematical."E. FORBES in Reports Brit. Assoc. 1843, p. 165.

+ Proc. Zool. Soc. 1836, iv. 116 and 119. § Rare and Rem. Anim. Scot. ii. 180.

Mem. p. 12.

vourer raises and shakes his papillæ in the manner that the porcupine shakes its quills when irritated, and then, laying back the dorsal tentacles, and curling up the oral ones, fixes the protruded mouth and jaws upon his prey, when, with a convulsive shrinking up of the body, morsel after morsel is appropriated. In this manner it is not uncommon to see an individual entirely devour another, half its own size. We have also seen this species feed upon a Lucernaria.”*

So also the pulmonated Gasteropods have a strange hankering after flesh, and become very cannibals in satisfying this propensity. Lister asserts that snails will eat not only bread and cheese, but flesh of all kinds, particularly fish and salted meat; and, in another place, he tells us that, having once placed an individual of the Helix aspersa with another of the Arion ater in a vessel together, he found, on the following day, that the former had slain the slug, and had miserably torn and eaten its skin, tantus animus est etiam pigerrimis animalibus." I have repeatedly seen the Black Slug (Arion ater) feeding on individuals of its own species which had been accidentally crushed, and were yet scarcely dead; and the observations of Mr. Power, which have been since confirmed, show that they feed voluntarily on earthworms, dead or dying. Of the aquatic tribes, we are informed by Mr. Jeffreys, that "the food of the Limnei is animal and vegetable matter in different states of putridity; which makes them deserve the perhaps not unapt epithet of 'scavengers of the waters.' In the absence of other nourishment, they will even devour each other, piercing the shell near its apex, and eating away the upper folds of its inhabitant. This accounts for the mutilated and often imperfectly repaired state of the upper volutions of some specimens." §

Relative to the times when molluscous animals feed, a very few facts only have been ascertained. Among the earlier naturalists it seems to have been a prevalent belief, that oysters and other bivalves were fat and in season at the full moon, and lean and out of season at the new moon.|| A. Gellius tells a story pat to the purpose :- "The poet Annianus, on his Falerian estate, was wont to spend the time of vintage in a jovial and agreeable way; and he had invited

* Brit. Nudibranch. Mollusca, pt. ii. pl. 12 and 15.

+ Exer. Anat. de Coch. 90. See also Mag. Nat. Hist. viii. 80. Anim. Ang. p. 114.

Lin. Trans. xvi. 371.

"Ostreis et conchyliis omnibus contingit, ut cum luna pariter crescant,

pariterque decrescant."-CICERO, De Div. ii. 14.