INHERITANCE IN HYDATINA 



55 



TABLE I 



Showing details of the parthenogenetic line C in figure 1. 

 designated cf 9 , female-producers 9 9 



Male-producers are 



Percentage of cf 9 



55.7 



when water was put on them. On September 9 one female 

 hatched, from which was bred the parthenogenetic hne desig- 

 nated C in figure 1 . The details of this Une are given in table 1 . 

 D. Females of line A were mated with males of line B on 

 June 24 and 25, 1911, and laid on the average 10.9 eggs apiece. 

 These eggs were dried and remained in this condition until August 

 30, when they were again covered with water. One female 

 hatched on September 2 and gave rise to line D of figure 1, the 

 details of which are shown in table 2. 



Viability in crosses and in inbreeding 



C X C. Females of line C were mated with males of the same 

 line October 22 to 26, 1911. From the 50 matings thus made, 

 805 fertilized eggs, or 16.1 per female, were obtained. These 

 eggs were kept under observation until December 20 to deter- 

 mine what proportion of them would hatch. Table 3 gives 

 the details of the hatching. It appears that 368 eggs, or 45.7 

 per cent of the whole lot, were viable. It is also worthy of 

 note that the number hatching daily gradually increased up to 

 the fifth or sixth day, and thereafter, with certain fluctuations, 

 decreased. Furthermore, practically the whole lot of viable eggs 

 hatched within a period of twelve or thirteen days, though the 

 eggs were kept much longer. The brief period in which the 

 hatching occurred is in such contrast with the case next to be 

 described that I have sought some method of measuring it. As. 



