INCUBATION 99 



cannot be successfully hatched together in the same 

 incubator, nor do the eggs of any two or more kinds 

 of fowls hatch well if placed together in the same incu- 

 bator or under the same hen. 



If the eggs are of uniform size, the temperatures of 

 all are equal or nearly so; if large and small eggs are 

 in the same machine the temperature may not be the 

 same in all. 



Eggs with white shells hatch in fewer hours than do 

 the dark-shelled eggs, for white shells are thinner and 

 transmit heat more freely to the germ within. Under 

 the same conditions, eggs with white shells will have 

 larger air cells than those with heavier shells. 



Only smooth and well-formed eggs should be used; 

 eggs with uneven surfaces, bad form, rough shells, or 

 mixed colors should be discarded, as well as eggs that 

 are abnormally large or small. 



Care of Eggs for Hatching. The best hatch is obtained 

 from eggs placed in the incubator the same day on which 

 they are laid. Eggs keep in prime condition for hatch- 

 ing up to the tenth day; if 2 wk. old they are safe for 

 incubation; but if older than this they seldom hatch 

 well, although some eggs that have been kept a month 

 will hatch. Eggs keep the best in a uniform tempera- 

 ture of about 55 F. in an atmosphere free from oil and 

 other bad odors. The vitality of eggs that are exposed 

 for any length of time to a temperature below 40 F. is 

 impaired. 



Eggs for hatching are shifted at least every other day 

 so that the yolks will not settle to one side, stick to the 

 shell, and thus destroy the germ. Preferably, the eggs 

 should be stored small end down, either in a regular 

 packing crate or any suitable receptacle. 



Eggs for hatching are injured if they are washed; 

 washing removes the natural glaze from the shell, and 

 such eggs do not hatch well. Though it is not advisable 

 to hatch dirty eggs, such eggs hatch better in soiled con- 

 djtion than they would if. washed. 



