n6 



ELIZABETH RAWLS. 



number of the offspring of this pair was 439, of which 308 were 

 females and 131 males, making a sex ratio of 2.3 : i. 



When this unusual ratio was first noticed, at the suggestion of 

 Professor Morgan, some of the flies that hatched out were mated, 

 the sisters with their brothers, in order to see whether the peculiar 

 ratio of the parents would be transmitted to any of the children. 

 Sixty-three pairs were made up and kept in good condition, each 

 female being allowed to lay all of her eggs, and the offspring of 

 each carefully separated according to sex and counted. Out of 

 the 63 pairs, 26 showed various high and in some cases unexpected 

 sex ratios, while 37 gave a normal ratio. The results are shown 

 in the following table: 



TABLE II. 



One of the first questions that arose was, whether the male or 

 the female was causing the peculiar ratio and to examine this 

 question the following experiments were carried out. The male 

 parent of the best line showing a ratio of 104 : i died before I had 

 a chance to breed him with other females, so the father of the 



