The Development of the Alligator 231 



lar area and the allantois begin to function, secures 

 a better aeration of the blood of the embryo. 



Around the embryo, during the stages that 

 precede the formation of the vascular area, is seen 

 an irregular area of a lighter color and a mottled 

 appearance. This area is bounded by a distinct, 

 narrow, white line, and varies in size from perhaps 

 a square centimeter to one third the surface of the 



yolk. 



During the earliest stages of development the 

 embryo is very transparent ; so that, as there is no 

 fixed place upon the yolk at which it may be 

 expected to occur, it is often very difficult to find. 

 Owing to this transparency, to the extreme delicacy 

 of the embryo, and to the character of the white, 

 the removal of an early embryo from the egg of 

 the alligator is a difficult operation and is accom- 

 plished only after some practice. 



The Development of the Embryo 



As the writer has pointed out elsewhere (59), 

 the embryo of the alligator is often of considerable 

 size when the egg is laid. This makes the obtaining 

 of the earliest stages of development a difficult 

 matter; so that the writer, as has already been 

 said, like S. F. Clarke (17), made three trips to the 

 South in quest of the desired material. Voeltzkow 

 (78) experienced the same difficulty in his work on 

 the crocodile, and made several trips to Africa 



