46 



BIOLOGY OF THE LABORATORY MOUSE 



Placenta 



Allantois 



Neural groove 



Yolk-sac 



Anterior intestinal 

 portal 



Neural groove 

 (anterior, open) 



Somites 



Fig. 25. — Photographs (X25) of mouse embryos. A. Lateral view of 7 day 18 

 hour, 6 somite embryo, with decidua and most of yolk-sac dissected. B. Dorsal view 

 of same embryo, amnion also dissected. C. 10 somite embryo, age Q-9^2 days. 

 Slightly retouched. Embryo from inbred stock. D. Same embryo as C, dorsal view, 

 amnion removed. 



