CRYSTALLINE STYLE OF LAMELLIBRANCHS. 95 



therefore with Berkeley that his conception of the respiratory 

 function of the crystalline style rests upon insecure evidence; and 

 I believe that this theory, interesting though it be, must be added 

 to the long list of the purely suppositious functions of the style 

 which have been proposed during the past two hundred and 

 thirty years. 



Bokmann ('23) figures the crystalline style and the style sac of 

 Mytilus chorus and his account agrees with the conclusions of 

 List and of Mitra. From a histological study of the ciliated 

 epithelium of the style sac he concluded that this must serve to 

 put the style in rotation, although he did not observe the move- 

 ment. This author apparently was not familiar with the work of 

 recent American investigators. 



A paper of much interest and valuable for its collection of many 

 observations under one head is that of Vonge ('23) in which for 

 the first time is given in one place an adequate account of the 

 mechanisms of feeding and of digestion in a bivalve mollusc. 

 This investigator traces the fate of food particles from the time 

 they enter the incurrent siphon until the waste is expelled from 

 the anus. No new information regarding the function of the 

 style is given in this paper, but the recent literature is well 

 summarized and a clear description is given of the role of the 

 crystalline style in digestion in My a. A study is made of the 

 effects of varying concentrations of enzyme and of substrate, 

 using the style and starch solutions. The optimum temperature 

 for the reaction was found to lie at approximately 32 C., with 

 complete destruction of the enzyme at 51 C. From the data 

 thus collected it is concluded that the powerful amylolytic ferment 

 of the style of Mya shows all of the characteristic properties of 

 such an enzyme. 



It is pointed out that the lamellibranchs may be arranged into 

 taxonomic groups on the basis of the morphology of the style sac 

 and intestine, but that such a grouping does not follow the 

 modern classification based on the gill structure. Yonge con- 

 siders that either our present system of classification is faulty or 

 that independent evolution has occurred within the digestive 

 system. I believe the latter to be the case since the morphology 

 of the digestive tract is to a high degree correlated with the food 



