JOHN W. GOWEN. 



beside that indicated above. The ratios which he reports for all 

 his data are 19 male, 24 male and female, and n female, the 

 methods adopted being such as to insure a random sample of the 

 general population of cattle twins. Cole 1 has also furnished data 

 on the sex ratios of cattle twins which he obtained from cattle 

 breeders' records of 303 twins. The ratios of these cattle twins 

 were 43 male, 165 male and female, and 88 females. Seven cases 

 of triplets were also reported. Besides these statistics the Maine 

 Agricultural Experiment Station has collected data on the fre- 

 quency of the different sexes of twins as they occur in Maine. 2 

 These twin births were born to services for which this station had 

 the service records. All services were traced in case the birth 

 record did not appear at the expected time and either the proper 

 birth record obtained, the cow found barren or the cow killed be- 

 fore parturition. These records should form a very homogeneous 

 set of data in which the sex of the twins was governed only by 

 chance. The data from these results show 5 males, 16 male and 

 female, and 5 females. The University of Maine Animal Indus- 

 try Department has always kept records of its herds since it was 

 established. These records should be a homogeneous set of data 

 wherein only chance was acting on the sex of the twin births as 

 the service dates and the disposal of all animals are known. The 

 ratio of the sex of these twin births in these data are 4 males, 4 

 male and female, and 3 females. These data summarized are 

 shown in Table I. 



TABLE I. 



SEX RATIOS OF TWIN BIRTHS IN CATTLE. 



1 Cole, L. J., 1916, "Twinning in Cattle with Special Reference to the 

 Freemartin," Science, N. S., Vol. 43, p. 177. 



- The cooperative data mentioned were collected by Dr. Raymond Pearl 

 while at this Station. The records for the college herd were obtained from 

 the Animal Husbandry Department by the author. 



