CRYSTALLINE STYLE OF LAMELLIBRANCHS. QI 



The only essential difference between Allen's results and mine is 

 that in fresh-water mussels he found that relatively little escaped 

 food was fed back into the stomach by way of the style, and he 

 concluded that this reclaiming function of the style was of 

 relatively little importance in these animals. The largest 

 amounts of such material were found in the core of the style soon 

 after regeneration of a new style had begun, an observation which 

 I can confirm in Anodonta grandis. The relative efficiency of this 

 retrieving mechanism in various bivalves will have to be ex- 

 tensively studied before we shall be in a position to determine its 

 importance to molluscs generally. The fact that Mya, Teredo, 

 Martesia and many other genera with a style sac nearly or quite 

 separated from the intestine are able to exist without such a 

 mechanism indicates that on the whole it plays perhaps a minor 

 role in nutrition. Phylogenetically it probably represents the 

 development of a strong recurrent tract of cilia situated in the 

 posterior part of the stomach of the ancestors of present-day 

 types; such a group of cilia as may, for example, be demonstrated 

 in the stomach of the larval oyster. 



Allen (/. c.) lays still further emphasis upon his conclusion of 

 1914, voiced likewise in my 1918 paper, that the crystalline style 

 arises in response to the presence of food in the stomach. Evi- 

 dence that such may not be the case is discussed further on in 

 connection with the findings of Berkeley ('23). 



Nogouchi '21 examined the crystalline styles of various marine 

 bivalves and gastropods for Cristispira, a large active spirochaete 

 which was first discovered in the style of the oyster. The 

 spirochaetes were found most frequently in Ostrea, next in Mya, 

 then in Modiolus; but not at all in Venus, Ensis, Mactra, Mytilus, 

 Pecten, Fulgur, and Nassa. Gross, however, has reported 

 Cristispira pectenis from the crystalline style of Pecten. Nogouchi 

 did not know of my 1918 paper in which is discussed briefly 

 the occurrence of Cristispira in the styles of certain bivalves and 

 its absence from others. Nogouchi observed that the style of the 

 oyster quickly liquefied after extraction from the body, and that 

 only oysters freshly removed from natural conditions contained 

 this structure. He believes that the great abundance of C. 

 balbiani in the oyster is due to the relatively soft consistency of 



