S32 PHYTIVOROUS MOLLUSCA. 



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 desti- 

 tute of teeth, a glandular ccecum of a pyriform shape. That 

 glandular ccecum differs obviously in its structure and form 

 from the structure of the liver. It consists of a single wide 

 cavity, studded internally with minute glandu]ar 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 inver- 

 tebrated animals possess a pancreas. Tiedemann has adopt- 

 ed 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. f 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 Tritoniae 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 Eolidse, 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 func- 

 tions 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. 

 f Lister Exer. Anat. de Coch. terr. p. 79, 80. 



