THE INCUBATION OF HENS' EGGS 215 



mentinp; ventilation has a profound effect upon the develop- 

 ing embryos. Dareste (as quoted by Eyclesliymer)' found 

 that when " all apertures of the incubator were closed during 

 incubation . . . nearly all the embryos died. It was 

 further found that there had developed in the albumen a 

 microscopic organism resembling the ordinary yeast plant." 



Gerloeh (as quoted by Eyclesliymer)^ found that by 

 diminishing the cjuantity of air during incubation he could 

 cause dwarfing of the embryo. On the other hand, when 

 shells were scraped very thin so that the supply of oxygen 

 to the egg was increased the embryos "developed at a 

 remarkably rapid rate, nearly twice as fast as in normal 

 growth . ' ' 



Eycleshymer^ took two incubators having similar venti- 

 lating systems, which were believed to be inadequate. One 

 was left as it was. The other was provided with two one-inch 

 intake pipes which extended outside the building, and were 

 so arranged that there was a continuous current of fresh 

 air passing into the egg chamber. Eggs from the same hens 

 were placed in each machine. The former hatched 44.3 

 per cent of fertile eggs while the latter hatched 85.7 per cent. 



\Vhile the foregoing shows unmistakably that there is a 

 ventilation problem it does not solve it. Common expe- 

 rience rather than experimental evidence must be depended 

 on in formulating our practice in ventilation. This is done 

 in the suggested routine of management (see page 2l'5). 



Position of the Egg. — It is generally understood among 

 poultrymen that the position of the egg during the period 

 of incubation has a profound inlhience upon the development 

 of the chick. It is a matter of common knowledge that the 

 head of the chick normally develoi)s at the large end of the 

 egg. As a usual thing, both in the nest and in the incubator, 

 the large end of the egg is uppermost. This is due to the 

 shape of the egg itself and possiL>ly by the lessening of the 

 specific gra\'ity of the large end as incubation proceeds, due 

 to the increasing size of the air cell. 



' Biological Bulletin, May, 1907. » Ibid. ' Ibid. 



