CRYSTALLINE STYLE OF LAMELLIBRANCHS. 97 



new data are given regarding the nature of use of the crystalline 

 style, the authors accepting the conclusions of my 1918 paper. 



In conclusion it is apparent that the main facts regarding the 

 origin, nature, and function of the crystalline style may be con- 

 sidered as quite firmly established and that we are now in a 

 position to attack with the aid of modern methods and the newer 

 knowledge of general physiology some of the problems of nu- 

 trition in molluscs. 



SUMMARY. 



The period of 74 days required for style reformation in Mya as 

 determined by Edmondson ('20) represents not only the time 

 during which a new style is regenerating after extraction, but also 

 the period of recovery following the rather drastic operation 

 performed by this investigator. From data procured from other 

 species of lamellibranchs it would appear that the time necessary 

 for actual reformation of the style is much less than the figure 

 given. 



It was shown (Nelson, '18) that owing to the imperfect mode of 

 separation of food particles from dirt and sand in the stomach of 

 bivalve molluscs, some undigested food materials may escape 

 down the intestine. In those forms in which the style sac is 

 incompletely separated from the intestine a part of this rejected 

 food material may be incorporated into the crystalline style, thus 

 eventually being returned to the stomach. The remainder pass 

 out undigested in the faeces. Failure to recognize this fact has 

 led at least two recent investigators to conclude that such living 

 organisms as are recovered from the faeces cannot be utilized by 

 the molluscs as food. 



The degree of solidity and of resistance to dissolution of the 

 crystalline style are suggested by Nogouchi ('21) as factors 

 controlling the presence or absence of Cristispira. That the 

 solidity and the resistance of the style are not the primary factors 

 involved in the distribution of Cristispira is shown by the presence 

 of these spirochaetes in the styles of Ostrea and of Mya which 

 represent respectively minimum and maximum hardness. 



Martin ('23) showed that a style may arise in Ostrea as a direct 

 response to siphoning in aerated water even when the incoming 

 water is devoid of all net and nannoplankton or other sources of 



