Distribution, Food and reproductive Capacity of some fresh-water Amphipods. 7 



Banta observes (1907) that in Mayfield's Cave, Indiana, E. gracilis 

 appears to breed at all seasons, adults with the young in the brood 

 pouch having been found throughout the year. No water temperatures 

 are given but he indicates that the temperatures of the air in remote 

 parts of the cave have a yearly range from about S** to 12^ C. In a 

 spring fed pool along the Lehigh Valley R. R., tracks near Ithaca, N. Y., 

 large numbers of E. gracilis were found breeding February 16, 1910. 

 The temperature of the water was 8" C while that of the air was 

 — 8* C. Again in the previously mentioned trout brook near Auburn 

 New York individuals of the same species were found breeding abun- 

 dantly as early as January 8, 1909 and January 22, 1910. The tem- 

 peratures of the water upon these dates were 6® and 8* C respectively. 



The last three species mentioned in Table 11 seem not to be 

 affected in their breeding by compartively high temperatures. Mated 

 pairs and females with eggs and young were found throughout the 

 summer in certain marsh pools and lagoons near Ithaca, the tempera- 

 ture of which remained between 23^ and 30® C during a greater part 

 of the period. When placed in balanced aquaria they continued to 

 breed from early March until late August. 



Gammarus limnaeus acted quite differently. Adult females with 

 oggs when placed in balanced aquaria in July, died within a few days. 

 Those so treated in January continued to breed in captivity until the 

 fore part of March when the temperature of the aquaria approached 

 18* C. These same females, however, continued to live and apparently 

 feed normally until late in June. 



In the following table III are recorded the highest and lowest 

 water temperatures together with the average of some twenty-six 

 readings taken during the reproductive period of each species. However, 

 in the case of G. limnaeus it was not possible to take a large enough 

 number of readings to deduce an average representing the true conditions. 

 Consequently the temperature given in the table for the average is in 



reality the mean^). 



Table HI. 



*) It should be remembered that the brook where the observations upon G. 

 limnaeus were made, is a cold spring trout brook and near its source only slightly 



