MODIFICATION OF REPRODUCTIVE PROCESS 75 



provides it with an ample supply of food, so that it does 

 not have to get into the outer world and fend for itself 

 until a very late stage in its development. Thus a watery 

 environment is no longer necessary for the early fish-like 



FIG. 44. 



Diagram illustrating the contents of a Hen's egg which has been incubated for 

 twelve days. The young bird is seen within the cavity of the amnion. Attached 

 to its lower side are seen two stalks -the hinder one connected with the allantois 

 (all) which lines the shell, the other with the yolk-sac in which the yolk (y) is con- 

 tained, alb, remains of albumen or white. (From Graham Kerr's Embryologv, 

 after a figure by Lillie in his Development of the Chick.) 



stages, for these are passed through in the interior of the 

 egg-shell. 



Then the body of the young bird comes to be enclosed 

 in a thin bag filled with watery fluid, and known as the 

 Amnion (see Fig. 44), which forms a water-jacket to pro- 

 tect its delicate substance from the jars to which its being 

 on land exposes it. 



Again, a bladder-like organ the Allantois (Figs. 44 

 and 45, all) bulges out from its body and flattens itself 



