GENERAL PRINCIPLES OF BREEDING. 85 



Several other theories have been advanced, 

 but the foregoing are among the principal ones. 

 It inay be that several of these causes have 

 some influence in determining the sex, but it is 

 quite certain that some of them, notably the 

 4th, 6th, and 7th, can have no influence what- 

 ever, and that none of them can be depended 

 upon. Nature has wisely provided, in order to 

 preserve an equilibrium in the sexes, that their 

 determination should be placed beyond the con- 

 trol of any single cause. It is known that some 

 males get a large preponderance of one sex or 

 the other, and that some females will produce 

 one sex only; sometimes, for a series of years, 

 the observations of one man will tend to con- 

 firm a certain' theory of sex production, while 

 in other hands the same theory will utterly 

 fail. Taking up at random Part I of Vol. V of 

 the English Short-horn Herd Book I find not 

 less than thirteen cows that have produced five 

 calves or over, the entire produce being of one 

 sex. In two of these cases three different bulls 

 were used, in eight cases four different bulls, 

 and in two instances six different bulls. Some 

 very remarkable cases were noted : The cow 

 Ann by Abraham (2905) dropped nine bull 

 calves in succession, the last two by Belshazzar 

 (1703), and then her tenth calf, also by Bel- 

 shazzar, was a heifer. Dorothy by Fisby (1040) 

 dropped six bull calves in succession by four 



