176 



FIRST BOOK OF ZOOLOGY. 



o 



A B C 



FIG. 154. EMBRYO BIRDS IN VARIOUS STAGES OF DEVELOPMENT. .4, Chipping Sparrow; 

 , Petrel; 7, Tern seen from above. 



If, now, the bones of the wing of an embryo bird be ex- 

 amined, the bones of the extremity of the wing, instead of 



humerus 





metacarpus 



phalanges 



FIG. 155. EIGHT WING OF AN EMBRYO BIRD GREATLY ENLARGED. Only a portion of 

 the humerus is seen. 



