THE INCUBATION OF THE EGG 213 



was more efficient in limiting the evaporation of eggs during 

 incubation than was a tray of the same size and location 

 filled with water. 



The average loss of weight by evaporation was 16.13 per 

 cent, when no sand was used and but 12.28 per cent, when 

 it was used. This seems to indicate that the sand furnishes 

 a more efiicient evaporating surface for moisture than does 

 the unbroken surface of the water. 



Pearl' reports that "The most satisfactory way to supply 

 this extra moisture where sand trays are not an integral part 

 of the incubator, has been found to be by sprinkling the 

 eggs with warm water twice a day. The water is warmed 

 to a temperature of from 104° to 108° F. . . . The 

 application of moisture is begun %,s soon as the eggs go into 

 the machine, and is continued until the 18th day. Since 

 adopting this procedure a very considerable reduction in the 

 mortality of chicks in the shell has been effected." 



Ventilation. — ^The question of what constitutes proper 

 ventilation for an incubator is one upon which there is little 

 satisfactory experimental evidence. Yet restricting or aug- 

 menting ventilation has a profound effect upon the develop- 

 ing embryos. Dareste (as quoted by Eycleshymer)^ 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." 



Gerloch (as quoted by Eycleshymer)' found that by 

 diminishing the quantity 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 oth'er was provided with two one-inch 



' Poultry Management at the Main Station, 1913. 



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



