314 THE LIFE OF A BIRD. 



escapes with readiness from its prison. Occasion- 

 ally, the chick is glued to the shell, and gentle 

 separation has been found useful; but in the 

 generality of instances it is best to leave all to 

 the natural method, and the chick will very 

 commonly make its own way best and safest out 

 of its prison-house. A very little injury inflicted 

 on the chick at this juncture proves fatal to it. 



It need scarcely be remarked before closing 

 this chapter, that all eggs are not necessarily pro- 

 ductive. If a fertile egg be kept beyond a cer- 

 tain time, it cannot any longer be reared either 

 naturally or artificially to give birth to a chick. 

 Even the earliest development of the chick will 

 not take place. It appears that by constantly 

 turning every day during the time they are kept, 

 eggs fit for incubation may be preserved in that 

 state longer than they would otherwise be. If 

 this is correct, it is difficult to account for the fact: 

 the common explanation given is, that the turning 

 prevents the adhesion of the contents of the egg 

 to its lining membrane. As to the secret alluded 

 to in a previous paragraph, it is impossible to state 

 its nature ; but it is probably some simple process 

 like that just mentioned, combined with keeping 



