Fifteen years' breeding behind these large, lusty, vigorous males 



ment, it seems unreasonable. Wild birds exchange places in keeping 

 the eggs warm continually. Also pigeons alternate their work during 

 incubation period, not allowing eggs to get cool. The hen under domes- 

 tication has no mate to help .her out and is forced to do the incubation 

 alone, while her polygamous husband takes care of the harem. This 

 necessitates that the hen either starve or go off the nest at periods for 

 food, taking a chance that the tiny germ will stand the exposure until 

 her return. The germ may suffer some from this exposure, and on the 

 other hand may also get used to this periodic cooling until it becomes 

 a law in its development. Evolution is a wonderful thing and adapta- 

 tion plays a great part in the unfolding of life. 



The question of moisture is also a problem in artificial incubation. 

 The egg contains enough moisture to carry it through the incubation 

 period if we could get our mechanical heating devices so perfected 

 that the egg would have practically the same conditions that it does 

 under the hen. But it is hard to adjust the ventilation so as to get 

 enough air and yet not dry the egg too much. An egg loses weight in 

 the open air very fast. The ideal incubator would have an egress for 

 the carbon dioxide thrown off by the egg and yet have no draft. These 

 conditions are hard to adjust. The egg wants a dead air space for 

 incubation and yet have some way to get rid of the gases thrown off. 

 In most of our artificial incubation moisture is supplied especially at 



51 



