ANIMAL BRKEDING 103 



develops according to the inherent tendencies which it received 

 at conception. And that the womb of the dam is only a dwell- 

 ing place for the foetus and a means for it to get nourishment. 



BREEDING FOR SEX 



The subject of sex determination has long been a popular 

 subject for experimentation and discussion. A great many- 

 theories have been advanced by which it has been said that the 

 sex of the offspring could be determined, but practically all 

 of them have been disproved or found not to hold good. 



The latest theory brought out in this connection has not 

 as yet had time to be disproved or to be found untrue and also 

 agrees with some earlier statements. This is based on the 

 age of the sperm cell (time after discharge from male) when it 

 unites with the egg. It is generally understood that sire and 

 dam are mated or the dam is bred, at the time of the period 

 of heat. This is the time, as stated previously, when the 

 ripened egg comes to the womb to be fertilized. It is not 

 always known during what part of the period of heat the eggs 

 come down but sometimes it is said that it is during the last 

 part. The time may vary with different animals. If the 

 dam is bred during the last part of the period of heat, when 

 the egg is in the womb ready to be fertilized and the sperm cell 

 deposited by the male unites with it at once, while it is still 

 fresh, the offspring is supposed to be a male. But if the dam 

 is served during the early part of the period of heat and the 

 egg has not yet come down the sperm cell from the sire will 

 become stale. If the egg is fertilized by a stale sperm cell 

 (but, of course, before it dies) the offspring is said to develop 

 into a female. Sperm cells may live a day or more in the 

 womb of the female. 



According to this theory a fresh sperm cell will produce a 

 male and a stale sperm cell will produce a female. Or if the 

 breeding is done during the latter part of the period of heat 

 the likelihood of getting males is greater and if breeding is done 

 during the early part of the period of heat the offspring will be 

 more largely females. On account of probable variations in 

 indefinite factors it can be clearly seen that with animals at 

 least it would be impossible to produce all males or all females. 



