226 WILLIAM RAY ALLEN. 



presumable that river forms, if taken at the right times, demon- 

 strate a more periodic activity in response to the rise and fall of 

 the current, the degree of turbidity, etc. 



Nelson is probably in accord with these reservations concerning 

 the Unionidse, for he agrees (I.e., p. 100) that the formation of 

 the style is directly dependent upon the food supply. In the 

 marine forms the return of food through the style sac to the 

 stomach is considerable. In the Unionids the return of food 

 through the style sac has become reduced because the sac is 

 usually occupied by the style. 



The spiral character of the style, caused, as demonstrated by 

 Nelson, by its axial rotation, has been brought out nicely in three 

 ways in my observation : 



fa) A regenerated style in one starved Anodonta was found 

 to have a great deal of green matter throughout, and but a very 

 slight amount of style substance. It had grown to at least normal 

 diameter. When kept for a time the secreted portion dissolved 

 out, leaving the green cohering portion wrapped about the core 

 like the threads of a screw, or a lathe shaving. 



(&) A few whitish styles were boiled for a short time in strong 

 sodium hydroxide. They were much reduced, and the residue 

 was in the form of a close rope-like spiral. 3 The white appear- 

 ance had given place to the amber-green color characteristic of 

 most newly regenerated styles. 



(c ) The actual rotation of the style has often been observed. 



Examinations were frequently made of the food substances 

 which could be recovered from the core of more or less com- 

 pletely regenerated styles. The food never showed a perceptibly 

 greater degree of digestion at the stomach end than posteriorly. 

 It is not likely, therefore, that the digestive processes are much 

 furthered during progress through the style or style sac toward 

 the stomach. 



(b) The Feeding of Specific Substances. 



A series of experiments in feeding certain substances, and in 

 forced feeding by injection into the stomach, were undertaken 



3 Edmondson's ('20) figures of partially formed styles very well represent 

 these. 



