EFFECT OF ENVIRONMENT UPON HYDATINA SENTA. 



345 



Effect of Drying upon the Viability of the Fertilized Eggs. 

 Dried for a Short Period. A lot of cross-fertilized eggs eggs 

 laid by females of line B fertilized by males of line A of my former 

 experiments (Shull, 1913) were kept for seven weeks to allow 

 hatching to take place. Practically all the hatching occurred 

 in the second to fourth weeks of this period, almost none in the 

 last three weeks. The 446 eggs (about two thirds of the original 

 lot) which remained unhatched after seven weeks were divided 

 into two nearly equal groups. One half was allowed to become 

 dry December 8 and remain dry about 13 hours, after which it 

 was remoistened. The other half was kept wet. The subsequent 

 hatching of eggs from these two groups is recorded in Table X. 



TABLE X. 



Showing the Effect of Drying Eggs for a Short Period Upon the Proportion that Hatch 

 in a Cross-Fertilized Lot of Eggs of Hydatina Sent a. 



Observations necessarily stopped December 20, but it seems 

 likely that even more would have hatched among the eggs that 

 were dried. Drying for a short period either favors hatching of 

 eggs that would not otherwise have hatched or hastens the 

 hatching of eggs whose hatching would otherwise have been 

 spread over a long period. 



The above experiment was repeated with a lot of eggs from 

 the reciprocal cross of the foregoing- eggs laid by females of line 

 A fertilized by males of line B. The original lot of eggs was kept 

 seven weeks to allow of hatching. During the last three weeks 



