50 



i 



number in the short space of 21 days, that the parent fowls may 

 be kept under such conditions as 'the investigator may wish and 

 that these conditions may be varied at will, that the embryo may 

 be followed through all the stages of its development, you real- 

 ize at once what a field the poultry business presents for a study 

 of the problem of sex, and the business takes on a new dignity 

 and interest. 



Some very important facts bearing on sex have been gathered. 

 The point on which investigators are more fully agreed is that 

 nutrition has a profound influence upon sex. Beginning with 

 insects it has been found that if caterpillars are starved before 

 entering the chrysalis state the resultant butterflies or moths are 

 males, while others of the same brood highly nourished are 

 females. With bees, too, the relation between nutrition and sex 

 seems equally well established. Experiments with tadpoles, 

 which were supplied with a diet steadily increasing in sumptuous- 

 ness, showed a steady and corresponding increase in the number 

 of females produced. The proportion of females to males, which 

 was originally 57 to 43, rose steadily as the diet became more and 

 more highly nutritious, until out of 100 tadpoles 92 were females 

 and 8 males. Coming up in the scale of life it has been found 

 that among mammals the same principle holds, although of course 

 other influences come in more than among the lower orders. 



Another feature that is believed to have an influence upon sex 

 is the time of impregnation. The fresher the ovum when fertil- 

 ized the greater the likelihood that the offspring will be a female. 

 If this conclusion is correct eggs laid at the beginning of a litter 

 should hatch a larger proportion of pullets than eggs laid later. 



The relative age of the parents is believed to affect the sex. 

 Where the male parent is the older the offspring are preponder- 

 atingly male ; and where the ages are even, or where the mother 

 is the superior in age, the preponderance is the other way. I find 

 that this is a theory quite generally held. I sometimes receive 

 letters from would-be purchasers asking for eggs from hens 

 mated with cockerels. It is a theory very easy to test, and the 

 reader should give it a trial in his yards." 



Temperature is also a feature to be reckoned with. I have 

 noticed in my own yards that in the cold months the proportion 

 of pullets hatched is smaller than it is later in the season. Take 

 the plant lice which multiply so rapidly upon the rose-bushes, 

 fruit-trees, and the like, and which are known to science as 



