98 



INCUBATION 



under two hens and supplying those hens from which 

 the eggs have been removed with other eggs. Vigorous 

 hens can endure the strain of the second hatching. 



The use of bull's-eye lamps, or lanterns, as shown 

 in Fig. 5 makes the work more efficient by magnifying 

 the germ, thus emphasizing the difference between the 

 living and the dead germs. When the egg is laid 

 against the opening with the large end up, the air 

 cell is seen at the top and the fertility or non-fertility 

 of the egg is readily perceived. The egg must fit 

 close against the rubber front so as to cut off the side 

 light. 



FIG. 6 



When held against the opening through which the light 

 comes, the clear, or infertile, egg is nearly transparent, 

 as shown in Fig. 6 (a). If fertile, the egg is opaque 

 and the embryo is plainly seen, as shown in Fig. 6 (&). 

 Some eggs show a brown shadow over the side as if 

 a veil were interposed between the shell and the 

 germ. The size of this apparent veil varies. Eggs 

 that have thick, dark shells do not show the veil so 

 plainly as do those that have thin or white shells. 



