EFFECTS OF INBREEDING ON THE SEX RATIO 



13 



TABLE 6 



Showing, by generation grovps, the sex ratios in the inbred and in the half-inl>red 



letters of the A series (male line) 



some eight points above the norm, it might appear that inbreed- 

 ing had tended to increase the relative number of males. Such 

 an interpretation of the results is not warranted, however, since 

 the sex ratio in the litters produced by the mating of unrelated 

 parents was higher than that in the litters obtained by the 

 mating of brother and sister, and since a similar increase in the 

 sex ratio was not found in corresponding litters of the B series 

 (table 7). 



As the females of the seventh generations that were used for 

 breeding were all taken from litters that contained an excess of 

 males, it is among their offspring that we may look for a possible 

 alteration of the sex ratio as a result of selection. The sex ratio 

 in the inbred litters of the eighth generation of the A series was 

 118.2cf : 100 9 . This sex ratio is very much lower than that 

 found in the inbred litters of the seventh generation (150 cT: 

 100 9), but it is still 13 points above the norm (105 a" : 100 9). 

 As examination of the records given in table 4 shows that in 



