FARMER'S CYCLOPEDIA OF LIVE STOCK 



certain. If an adult cock be mated with 

 not more than three pullets, the result 

 is very uncertain. If an adult cock be 

 mated with five or more pullets, the pul- 

 lets are generally in excess. The fewer 

 hens and the more vigorous the stock, 

 the greater is the proportion of cockerels 

 which are always more numerous in the 

 earlier eggs of a season than the later." 

 But, as argued by Miles, Wright ad- 

 mits that "there will be numerous and 

 startling exceptions to these rules." 

 They, therefore, fail to have the value 

 of a general law. 



Food and sex — Many writers have 

 maintained that sex is determined by 

 nutritive conditions. According to this 



of heat to pass after the birth of a 

 heifer calf before the bull is admitted 

 for service. This hypothesis in turn 

 does not agree with actual experience in 

 breeding. Schenk's theory of the deter- 

 mination of sex is that each sex has a 

 tendency to produce the opposite sex. 

 The stronger, more vigorous or better 

 nourished parent should therefore pro- 

 duce the opposite sex in the offspring. 

 The facts are not in harmony with this 

 theory. 



No SATISFACTORY THEORY Although 



much speculation has been indulged 

 in regarding the factors which deter- 

 mine sex, none of the theories proposed 

 is perfectly satisfactory, and no scheme 



Fig. 23 — OLD ENGLISH HOG THE BASIS OF MANY MODERN BREEDS 



idea the sex is not determined at the 

 time of union of the germ cells. This 

 notion receives some support from the 

 phenomena observed in bees. Ordinary 

 bee larva? which, if fed in the usual 

 way, develop into sexless working bees, 

 may be made to develop into queens by 

 feeding on "royal jelly." This would 

 indicate that the sex is not determined 

 until the embryo has undergone some 

 development. 



Stuyvesant proposes a theory based on 

 the assumption that the dam entirely 

 controls the sex of the progeny, and that 

 every alternate egg is of the same sex. 

 If heifer calves are desired, it would 

 merely be necessary to allow one period 



has worked out successfully in practice. 

 Statistics compiled at the Maine experi- 

 ment station on 3614 calves do not tend 

 to substantiate any theory of sex deter- 

 mination. Some cows show a tendency 

 to produce bull calves, others heifer 

 calves. The same is true of ewes, mares 

 and sows. It seems to be an individual 

 matter and is not under the control of 

 man. 



Having discussed the various factors 

 of variation which may be brought to 

 bear on the germ cells before and at the 

 time of their union we may proceed to a 

 consideration of influences which affect 

 the developing embryo and the growing 

 young animal. The importance of the 



