STUDIES ON THE CELLS OF CATTLE. 



303 



trolling sex, including the one in relation to time of service which 

 is commonly practiced by animal breeders, must be abandoned. 

 There is considerable literature on the metabolic theories of 

 sex-determination which will not be discussed here. However, 

 reference may be made to the brief though able discussion of this 

 subject by Babcock and Clausen ('18). 



IX. SEX RATIO IN CATTLE. 



It might be well to quote here Pearl's ('17) more recent results 

 of extensive studies on the control of the sex ratio in cattle. 

 He says: "Some earlier statistics appeared to indicate that there 

 was a possibility of influencing the sex ratio by paying attention 

 to this point. It was believed to be of such extreme importance 

 as to justify the careful study of the matter on the basis of much 

 more extended statistics. These statistics we have now collected 

 and analyzed and shall publish as soon as possible. In the mean- 

 time it may be reported that, with the more extended statistics 

 in hand, it appears to be conclusively established that there is no 

 definite or permanent relation between the time in the heat period 

 at which the cow is served and the sex of the offspring. The 

 apparent relation between these two factors, which is believed 

 by many breeders to exist and which our earlier statistics ap- 

 peared to indicate, seems now to be purely accidental, and to 

 have arisen only because of the comparative meagerness of the 

 statistics on which the matter was discussed. 



TABLE II. 



SHOWING THE SEX OF THE CALVES FOLLOWING SERVICE AT DIFFERENT PARTS OF 



THE HEAT PERIOD. 



'The summarized results of 1 ,313 separate and distinct matings 

 given in Table II. will demonstrate this point. In each one of 

 these 1,313 cases the following facts were accurately known, and 



