i8 



EARLY EMBRYOLOGY OF THE CHICK 



Pig. 5. — Surface aspect of blastoderm at various stages of cleavage. (Based 

 on Blount's photomicrographs of the pigeon's egg.) The blastoderm and the 

 immediately surrounding yolk are viewed directly from the animal pole, the 

 shell and albumen having been removed. The order in which vthe cleavage 

 furrows have appeared is indicated on the diagrams by Roman numerals. 



A, first cleavage; B, second cleavage; C, third cleavage; D, fourth cleavage; 

 E, fifth cleavage; F, early morula. 



