their Food and Digestive -Organs. 79 



of bivalve shells, the large perforations leading from the cavity 

 into the substance of the liver. Here, again, we observe the 

 short, wide hepatic ducts, bearing the same general character 

 which they have from the lowest of the Mollusca up to the 

 class of fishes. Baron Cuvier remarks, that it is surprising 

 the vegetable food does not gain admission from the stomach 

 into the cavities and substance of the liver. I have collected 

 many of those animals upon our coasts, and have opened 

 them in all conditions as regards food taken into their stomach, 

 and I have found the stomach often completely filled with 

 minutely divided portions of coarse marine plants ; but I never 

 found them with their stomach thus filled, without finding 

 that the hepatic ducts were also filled with the food. These 

 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 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 con- 

 sider 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." 

 {The Lancet, No. 572. p. 708, 709.) 



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 * ; and, even so 



* " Ostreis et conchyliis omnibus contingit, at cum luna pariter cres- 

 cant, pariterque decrescant." (Cicero, Be Biv., ii. 14.) 



