EFFECT OF ENVIRONMENT UPON HYDATINA SENTA. 



347 



The foregoing experiment was repeated with inbred eggs of a 

 line that regularly hatched more than half its eggs. The eggs 

 remaining unhatched after five weeks were divided into two lots, 

 one of which was dried over night and then remoistened. Though 

 both were kept three weeks, not one egg in either lot hatched. 

 Drying neither increased nor hastened the hatching. 



Dried for Periods of Moderate Length. These experiments 

 differed from the foregoing in that all of the eggs were dried in 

 one half of the experiment, instead of only those which failed to 

 hatch under ordinary conditions. Inbred eggs were used, and 

 drying occurred about the time when hatching was due to begin, 

 that is, a week after the eggs were laid. Hatching began three 

 or four days after the eggs were remoistened. Observations 

 were continued for a month after remoistening. One lot of eggs 

 was kept wet as a control, one was dried over night, one dried 

 two weeks, and a fourth dried four weeks. The experiment was 

 performed three times. The totals, without daily records, are 

 given in Table XIII. The second division of this table really 

 belongs to the preceding section of this paper, since it involves 

 only a short period of drying, but it seems best to retain it here 

 for the sake of comparison. 



TABLE XIII. 



Showing the Effect of Drying for Various Periods Upon the Viability of the Fertilized 

 Eggs of Hydatina Senta. Inbred Eggs Were Used. 



There is plain indication in these results that drying, even for a 

 short time, reduces the number of eggs that will hatch when again 

 placed in water; and that the longer the period of desiccation, 

 up to the limit of complete inhibition, the fewer the eggs that 

 hatch. 



