18 



G. C. Embody. 

 Table VH. 



H.limnaeus 



H. fasciatus 



Hyalella 



] st moult 



Deposition of eggs 



Hatching 



Young left pouch 



2iid moult 



2^^ set of eggs 



Hatching 



Young lef- pouch 



3rd moult 



B^^ set of eggs 



Hatching 



Young left pouch 



Average recurrence of oviposition 

 Average recurrence of moulting . 

 Average mean daily temperature . 



Dec. 31 



Jan. 1 



„ 22 



„ 26 



2 



3 



24 



27 



4 



Feb. 



Mch. 



33 days 

 31,5 „ 

 14,4" C 



July 12 

 / 12 

 „ 20 

 „ 22 



n 23 



„ 23 



. 31 



Aug. 2 



2 



2 



„ 19 



. 2 



11 days 



10,5 , 



26,60 c 



July 5 

 . 5 

 . 13 

 , 15 

 , 15 

 « 15 

 . 23 

 „ 24 

 „ 25 

 . 26 



Aug. 3 

 . 5 



10,5 days 



10 „ 



240 C 



ing the same number of moults. It is also indicated that the average 

 period of recurrence of ecdysis is very nearly equal to that of ovi- 

 position, a fact which will be of assistance in determining the possible 

 number of sets produced by a single female during the total reproduc- 

 tive period. 



3. Moulting of Adults. 



During the fall of 1909 and winter of 1910 a female each of 

 Hyalella and G. fasciatus were isolated in dishes as has been pre- 

 viously described and the rate of moulting observed. 



The two moulted as follows: 



Hyalella. 



ist moult. 2d 3d 4 til 5 til 6^^ 



Nov. 24, Dec. 10, Dec. 24. Jan. 11, Jan. 26, Feb. 9. 

 Period = 16 dys., 14 18 15 14 



G. fasciatus. 

 l8t 2d 3d 4th 5th Qth 7th 8tli 9th 



Nov. 1, Nov. 16, Nov. 24, Dec. 8, Dec. 23, Jan. 6, Jan. 20, Feb. 8, Feb. 27 

 Period =15 dys., 8 14 15 14 14 19 19 



Comparing the data thus secured, it was thought that by keeping 

 a record of the daily mean temperatures of the air in the immediate 

 vicinity of the aquaria, a partial correlation of temperature with the 

 rate of moulting might be disclosed. A number of females of each of 

 the four species were therefore placed in as many dishes and their rates 

 of moulting, together with the mean daily temperature of the room 

 were recorded. 



