lo4 PHYSIOLOGY OF THE INVERTEBRATA, 



contains about five per cent, of solids, and readily digests 

 fibrin and hydrolyzes starch. 



Similar reactions to the above are also produced by the 

 so-called livers of Homams and Palmmon. There is no doubt 

 that the " liver " of the Macroura is a true pancreas. 



The Lamellibeanchiata. 



Dr. Leon Fredericq has investigated the alimentary canal 

 oiMya arcnaria (see Fig. i8) and Mytilus edulis (the mussel). 

 The secretions of the -so-called livers of these two animals 

 digest fibrin analogous to the pancreas of higher forms.* 

 When neutral and alkaline extracts of the organ are prepared, 

 they have the characteristic reactions already given under the 

 head of Carcimis mmnas ; but Fredericq states that he has 

 extracted glycogen from the secretion of the " liver " of Mi/a. 

 It is, however, probable that glycogen is only present in 

 this organ and other tissues of Mya during certain periods 

 of growth. It may be remarked that in Carcimis, where 

 development is achieved by sudden bounds — by moultings — 

 the " liver " contains glycogen during these periods of rapid , 

 growth, but at other times there is not the slightest trace of 

 the carbohydrate in that organ or any part of the alimentary 

 canal. 



The contents of the digestive canal of Mya are acid. This 

 acid is chlorohydric acid, and is found chiefly in fluids obtained 

 from the stomach. It is possible that the function of the 

 stomach, as a separate digestive organ, becomes more difEer- 

 entiated in the Zaniellihranchiata. Is it possible that it gives 

 rise to a secretion similar to the gastric juice of higher 

 forms ? 



The so-called liver of Ostrea, Pecten, Anodonta, and Cardium 

 functionates as a true pancreas. 



Dr. C. A. MacMunrut has extracted enterochlorophyll from 



* Proc. Poy. Soc. Mdi^., vol. 14, p. 237. 



f PJiilgsophical Transactions of Rmjal Society, 1886, pt. i, p. 235. 



