RECENT CONTRIBUTIONS TO THE KNOWLEDGE OF 

 THE CRYSTALLINE STYLE OF LAMELLIBRANCHS. 



THURLOW C. NELSON. 

 (From the Zoological Laboratory of Rtitgers University.) 



The crystalline style of pelecypod and of gastropod molluscs 

 has long been a fascinating subject for investigation by students 

 of these groups. In a paper (Nelson, '18) published six years ago 

 the attempt was made to summarize and to analyse the more 

 important contributions which had appeared up to that time, and 

 by original observation to solve some of the problems regarding 

 the origin, nature, and function of this structure. The con- 

 clusions of Coupin, 'oo, Mitra, '01, and others, that the crystalline 

 style contains strong amylolytic ferments, were confirmed. In 

 addition the style was shown to have at least two other functions. 

 The first and more important of these is the role played by the 

 style in the separation of food materials from sand and other 

 waste. The powerful cilia of the style sac spin the style around 

 on its long axis while pushing it anteriorly into the stomach. 

 The head of the rotating style gathers the food strings coming 

 from the oesophagus and as the whole mass is whirled around in 

 the stomach much of the sand and other non-digestible matter is 

 sorted out mechanically by the ciliary tracts of the stomach wall, 

 and passed on into the intestine. At the point where the head of 

 the revolving style comes into contact with the anterior wall of 

 the stomach there is developed a tough resistant covering which 

 I named the "gastric shield" (fleche tricuspide of Poli, 1791). 

 The importance of such a sorting and stirring mechanism in 

 animals in which ciliary activity has completely replaced muscular 

 peristalsis, was pointed out. 



In forms such as most of our common bivalves, where the style 

 sac is incompletely separated from the intestine by two ridges or 

 typhlosoles, an additional function is served. Food particles 

 escaping from the stomach may be passed across the faces of the 

 typhlosoles from the intestine and then be incorporated into the 

 style. Most of such returned material enters the style sac near 



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