304 J. E. WODSEDALEK. 



reported in such a way that any bias, conscious, or unconscious, 

 of the observer could not have influenced the result: (a) the 

 time in hours from the first appearance of heat (oestrum), as 

 noticed by the breeder, to the time the cow was successfully 

 served; (&) the sex of the calf resulting from this service. 



"It is evident from this table that there is no significant 

 preponderance of females when service is early in heat. There 

 is not now known any method by which the sex ratio or propor- 

 tion of the sexes in cattle may be effectively controlled by the 

 breeder. A more detailed account of the results, together with 

 further statistics will be published elsewhere." 



X. SEX-LIMITED INHERITANCE IN CATTLE. 



The discovery of the remarkable behavior of certain characters 

 in heredity which can only be plausibly explained by supposing 

 that they are linked with a sex-chromosome or a sex-determining 

 factor still further strengthens our belief in the existence of such 

 a definite factor. Wentworth ('16) reported a case which seems 

 to fall under this general sex-limited group in the inheritance of 

 black-and-white in Ayrshire cattle. While the general breed 

 color is red-and-white, black-and-white animals have been known 

 for some time, as shown by Kuhlman ('15). It is difficult to 

 state whether the black is due to a true black pigment or whether 

 it is simply a very dense red, since chemical solutions have not 

 yet been attempted. 



In summarizing the results of the different crosses, Wentworth 

 says, "If the factor of the black-and-white color is represented 

 by B, the hereditary constitutions are as follows: BB is always 

 black-and-white; bb is always red-and-white; Bb is always 

 black-and-white in the male and red-and-white in the female. 

 All of the nine possible matings were discovered, as shown in 

 Table I. 



"The expectations here presented are based on the most 

 probable result of each of the matings, considered on an indi- 

 vidual basis with reference to the number of animals produced 

 by each type of mating, but without figuring the proportions of 

 the sexes as equal. From these data it would appear that the 

 black-and-white color of Ayrshire cattle behaves in an ordinary 



