84 AMERICAN JOURNAL 



Canal and Mohawk River, at Mohawk, N. Y. In the river, 

 where food seems to be less abundant, there are very few ab- 

 normal specimens, and these few belong to rufa, and consist of 

 the gibbous form previously mentioned. I have been led to 

 suspect that the gibbous phase may be in some way associated 

 with some modification of the function of nutrition as influenced 

 by the abundance or scarcity of appropriate food. With an 

 excess of food might there not be an excessive development of 

 some organs ? And on the other hand, might not those organs 

 be less largely developed with a somewhat restricted supply of 

 food? 



We will see what the evidence is from the shells found in the 

 Erie Canal. There is one portion of the canal that seems to be 

 especially favorable for the development of 31. Integra, Say. 

 It has abundance of food, a soft bed of mud mingled with de- 

 composing vegetable and animal matter, and a favorable tem- 

 perature. The greater number of the shells are in water from 

 seven to nine feet deep. At this favorable point are thre'e spe- 

 cies associated — 31. Integra in thousands, 31. decisa in hundreds, 

 and 31 rufa in dozens, few and scattered. 31. rufa exhibits no 

 remarkable features except fine development. 31. decisa ex- 

 hibits no unusual phases of development. 31. integra riots in 

 luxury, and, besides producing an immense number of shells 

 varying but slightly from the typical form, produces gibbous 

 specimens in considerable numbers, but Avithout any uniformity 

 in size, form or proportions. There is one form, however, that 

 may in one respect be regarded as a typical variation, from which 

 many of the other forms may be regarded as modified deviations. 



The typical variation seems to be an exaggeration of the func- 

 tions of the female — as it consists in a more ample expansion of 

 the whorls just below the suture, the shell becoming contracted 

 somewhat a little lower down. The enlargement corresponds to 

 an expansion of the shell to accommodate a distended ovarian 

 sac ; it has no specific character. 



Several years ago, one spring, at the time the canal was emp- 

 tied for repairs, I succeeded in obtaining about thirty specimens 

 having a very uniform character in one particular. Their uni- 

 form resemblance in this respect led me to believe they might be 

 the common offspring of one parent. These specimens were all 

 characterized by being somewhat elongate in the direction of the 

 axis, and by having a portion of the shell which should be ap- 

 pressed to the preceding whorls at the suture, everted and eroded. 

 Since that time no other specimens of that character have been 

 found. 



I have, at the present time, a single specimen of integra in 



