Distribution, Food and reproductive Capacity of some fresh-water Amphipods. 19 



The data secured in this maimer are condensed in the following 

 table. They are more or less fragmentary but in a general way will 

 serve our purpose. 



Table VIU. 



It can be seen that in general the period between moults increases 

 as the average mean daily temperature decreases. However the in- 

 dividual variation is so great and the data so few that no definite 

 relation between the two can be estabhshed. Miss Mary T. Harmon 

 gives (1907 pp. 70 — 75) some observations upon the rate of moulting 

 of several individuals of Gam mar us (sp?) kept in glass jars between 

 July 8 and August 10, which had been variously operated upon. In 

 some cases the right hind leg had been removed in others, both hind 

 legs. According to her statements, when one hind leg had been severed, 

 the average rate of moulting was fifteen days with extremes of twelve 

 and twenty- three days; when both hind legs had been so treated, the 

 average was sixteen and two-sevenths days with extremes of twenty 

 and thirteen. We are not informed however, as to the temperature 

 conditions nor is any statement made concerning the rate of the moul- 

 ting of unmutilated specimens. 



9. Moulting of Young. 



Eggs of three species, G. limnaeus, E. gracilis and Hyalella 

 were placed in different watch glasses just prior to hatching. The 

 resulting young were separated in other watch glasses, each one of the 

 latter having a serial number. The time between hatching and the 

 first moult together with the mean daily temperatures were recorded. 

 The results are presented in the table which follows. 



