TRIPLET CAIvVKS. 28 1 



liead pattern she is homozygous for the absence of white face. 

 Let us assume this to be the case, and also assutne" that she 

 is heterozygous, with reference to body color, the Guernsey 

 fawn being the assumed dominant over red. 



Then we may suppose the male of the triplets to be a homo- 

 zygous recessive with reference to colored face, and a hetero- 

 zygous dominant in respect to body color (Guernsey). The 

 females of the triplets on this assumption would be heterozy- 

 gous with reference to face pattern (the dominant white face 

 showing) and pure recessives relative to body color. The only 

 way, of course, to have tested the validity of these assumptions 

 would have been to have bred the triplets and examined their 

 progeny. While the male was bred back to his dam, I was not 

 able to get any information as to the color or pattern of the 

 progeny except that all were alike in these respects. This would 

 be expected on the hypothesis made so far as face color is 

 concerned since the son and his dam were supposed pure reces- 

 sives with reference to Colored face. In regard to body color 

 the case is more difficult but it is useless to speculate in the ab- 

 sence of more detailed data regarding the ofifspring. 



Summary. 



In the introductory portion of this paper there is presented 

 a discussion of the general biological problems on which cases 

 of multiple gestation in normally uniparous animals bear. The 

 •essential purpose of this discussion is to suggest points on which 

 information should be collected by those having an opportunity 

 to observe such cases. These are : 



(a) The physiology of multiple gestation. 



(b) The determination of sex. Young from multiple gesta- 

 tions in normally uniparous animals exhibit marked and regular 

 deviations from the sex ratios observed in single births of the 

 some species. This fact is of significance in connection with the 

 question of the degree tO' which sex determination is an epi- 

 genetic phenomenon. 



■"^It is difficult to get data to test this assumption because of the rarity 

 with which pure Guernseys and pure Shorthorns or Herefords are 

 cross-bred. 



