II 



THE DOG'S EGG. 



83 



domestic utility; and wants the shell, which would 

 not only be useless to an animal incubated within 

 the body of its parent, but would cut it off from 

 access to the source of that nutriment which the 

 young creature requires, but which the minute 

 egg of. the mammal does not contain within itself. 



V.-'^ii-X^O" ' 



B 



' .~v; 





MHMSmS^^m^ my 



Fig. 13. — A. Egg of the Dog, with the vitelline mem- 

 brane burst, so as to give exit to the yelk, the germinal 

 vesicle (a), and its included spot (&).' B. C. D. E. F. Suc- 

 cessive changes of the yelk indicated in the text. After 

 BischofF. 



The Dog's egg is, in fact, a little spheroidal 

 bag (Fig. 13), formed of a delicate transparent 

 membrane called the vitelline membrane, and about 

 Y^-jj-th to y!~o-th of an inch in diameter. It con- 

 tains a mass of viscid nutritive matter — the yelk 



