Distribution, Food and reproductive Capacity of some fresh-water Amphipods. 23 



Table XL 



day six eggs were laid by each female. A third young female which 

 possesed enlarged dark colored ovaries was placed with a large male 

 which had just been separated from its mate. Mating was immedia- 

 tely accomplished and on the forty-fifth day, six eggs had been depo- 

 sited. Two other pairs mated and laid eggs at the age of fifty-one 

 days and still another female deposited eggs at the age of sixty days. 

 So far as could be determined the eggs of all young females developed 

 normally and hatched in due time. 



As a check upon these results, large collections of Hyalella with 

 eggs in their brood pouches were made. Only the smallest females 

 were kept and their lengths taken. In this maimer the smaller breed- 

 ing female was found to be 3,06 mm long and to possess six eggs. If 

 we examine the data for Hyalella in table XI and also the curve of 

 growth it is seen that the 3,06 mm female must have been approxi- 

 mately thirty-five days old. 



Collections of breeding females of the other three species were 

 made and the smallest ones measured, this furnishing the only available 

 means of determining approximately the ages of the youngest sexuaUy 

 mature females. If these data are likewise compared with those in 

 table XI and with the respective curves of growth, the approximate 

 ages at which individuals of each species reach sexual maturity may 

 be obtained. 



The results of the foregoing procedure may be conveniently tabulated 

 as follows in table XII. 



