EEGULATING SEX 19 



carded eacli and every such known scheme 

 for regulating sex. 



We have noticed, however, that, at cer- 

 tain seasons, there is a predominance of 

 male colts in our district and, at another 

 time, a predominance of female colts. At 

 the beginning of the stud season, we are 

 inclined to believe that male colts predom- 

 inate, but we have no positive proof. We 

 sometimes think that if a mare is bred di- 

 rectly after she has come in season male 

 colts will predominate, and as the season 

 advances female colts will predominate. 

 The difficulty lies in the fact that a breeder 

 can not always definitely ascertain the ex- 

 act date when a mare commences to come 

 in season. 



I have no doubt that I could breed 

 stallions and mares to produce only male 

 or only female colts by a continuous breed- 

 ing from sires and dams coming from 

 families that had produced only male or 

 female colts. In this way I produced a 

 herd of sheep that produced only twins or 

 triplets. Whenever you find twins in 

 humans, you will generally find an hered- 



