94 THURLOW C. XELSOX. 



style are so largely dependent upon the activity of the powerful 

 cilia of the style sac, it is to be expected that no style would form 

 in an absence of oxygen. From what we know also regarding the 

 oxygen consumption of the glands of mammals it may be assumed 

 that relatively little secretion of style substance would occur in an 

 absence of oxygen. Berkeley's work is open also to the objection 

 that nowhere does he mention having watched his molluscs to 

 determine whether they opened up and siphoned in the anaerobic 

 water. Such observations are imperative owing to "sulking" on 

 the part of some bivalves after handling, even when the sur- 

 rounding water is plentifully supplied with oxygen and food. I 

 find that the oyster will not open in oxygen-free water until it 

 becomes too weak to remain closed. Dissolution of the style 

 occurs when many species of bivalves remain tightly closed for a 

 few hours, irrespective of whether the surrounding water is 

 aerated. 



In connection with the relation between the degree of aeration 

 of natural waters and style formation it is of interest to compare 

 the crystalline style of Pisidium idahoense with that of Mactra. 

 Pisidium occurs in abundance in the mud at the bottom of Lake 

 Mendota, Wisconsin, where for two thirds of the year the water 

 may be completely devoid of oxygen (Birge and Juday, 'n, Cole, 

 '21). Mactra on the other hand lives in or close to the breaker 

 line along sandy coasts, where the water at all seasons of the year 

 is saturated with oxygen. The style of Pisidium is no larger than 

 that of other Cyrenidae w r hich live in relatively well aerated creeks 

 and ponds, whereas the crystalline styles of all Mactra which I 

 have examined are relatively large, firm, and among the best 

 developed of the styles I have found in any bivalve. 



In Ostrea the direct relationship of crystalline style secretion to 

 feeding can readily be demonstrated since this process assumes a 

 somewhat rhythmic character. During the flood tide when the 

 bivalves are feeding actively the style is large and firm, but by the 

 late ebb tide, at which time most of the sand has been sorted out 

 and removed from the stomach and digestion is well under way, 

 the style may be reduced to a soft amorphous mass of jelly. The 

 crystalline style is usually thin or entirely lacking at sunrise 

 before active feeding of the molluscs has commenced. I agree 



