72 



A. FRANKLIN SHULL 



same time, and hence not under the same conditions. Selection 

 affected viability, but this effect was all in the first selection, 

 and further selection did not increase the difference in viability. 



Effect of crossing on viability in two lines made different by 



selection 



Whether selection produced a permanent difference, or whether 

 the difference was maintained only by continuous selection, was 

 determined by the remaining experiments. First among these 

 were reciprocal crosses between the parthenogenetic lines in L2 

 and Ho. 



L2 X H2. Females of the parthenogenetic hne Lo (see fig. 1) 

 were mated with males of the hne H2 April 11 to 19, 1912. From 

 36 such females were obtained 427 eggs, of which 245, or 57.3 

 per cent, hatched before May 6, as in table 27.. 



TABLE 26 



Showing details of two parthenogenetic lines in Hz, figure 1, one derived jrovi a 

 family in which only 43.7 -per cent of the fertilized eggs hatched, the other from a 

 family in which 80.9 per cent of the eggs hatched. 



