PROGRESS OF INCUBATION. 271 



afforded to the egg, which it otherwise could not 

 have obtained. Once a day it is necessary also 

 slightly to damp the eggs with a soft sponge on 

 the top only, as they lie in the tray ; by this means 

 their loss by evaporation is in some measure re- 

 stored to them. 



After three days of incubation a round spot or 

 shadow may be seen at the top of the egg without 

 removing the shell, if the process has been success- 

 ful. This is the early development of the germ. As 

 the time goes on, the germ enlarges, and ultimately 

 fills the egg. Should some of the eggs placed in the 

 incubator be addled, they are to be distinguished 

 from the rest by, it is said, a ringing or hard sound, 

 when moved with the others; while the good eggs 

 sound very dull as if cracked. The suspected eggs 

 are generally withdrawn, as they might prove 

 injurious to the others. At the expiration of nine- 

 teen days and a half, the included chicks begin 

 to peck at their shells. Thus, if a number of eggs 

 were put in to incubate on a Thursday at five P.M., 

 on the Wednesday morning previous to the expi- 

 ration of three weeks, many shells would be found to 

 be cracked, and some chickens would even begin to 

 come out Those which have not broken through 



