CRYSTALLINE STYLE OF LAMELLIBRANCHS 107 



The presence of a style of great dimensions has been noted by 

 several workers in Teredo and other boring molluscs, and I 

 have found the same in Martesia. The relatively great develop- 

 ment of the style in these forms is probably connected with 

 their mode of feeding and living. 



Some of these molluscs bore into objects close to the high- 

 tide level, and are hence unable to feed for long periods. All 

 of them communicate with the exterior by means of a compara- 

 tively small opening. It is probable that their periods of feed- 

 ing are further disturbed by deposits of mud over these open- 

 ings, so that it is necessary to use to the best possible advan- 

 tage every opportunity for feeding. Such being the case, the 

 presence of a large amount of enzyme, ready for immediate use, 

 could not but be of great advantage to these molluscs. 



5. SUMMARY AND CONCLUSIONS 



In the present paper the attempt has been made to bring 

 under one head the results of all former workers regarding the 

 crystalline style of lamellibranchs and to settle important ques- 

 tions concerning its origin, nature, and function. 



A survey of the literature shows that much of the credit 

 given to Mitra ('01) rightfully belongs to Barrois ('89, '90) and 

 Coupin ('00). 



Anatomical features of the stomach and intestine of some 

 common lamellibranchs, not previously noticed, are pictured and 

 described. 



The mode of secretion and formation of the style has been 

 studied in marine and fresh-water forms. It arises as a thin 

 core of bubbly mucus, upon which are deposited co-axial layers 

 of a gelatinous protein, containing enzymes. 



Its embryological developrnent is followed in Ostrea and 

 Dreissensia. 



The ciliary mechanism of the stomach, intestine, and style 

 sac has been traced out in some detail. It was found that the 

 molluscs studied possess the ability of separating food from 

 foreign particles in the stomach by ciliary action. This mechan- 



