THE EARLY EMBRYOLOGY OF THE MOUSE 43 



Endocardium 



Exocoelom Amnion 

 \ 



Dorsal aorta 



Sinus venosus 



Coelom' 



Fore -gut 



Endocardium 



Pericardial 

 coelom 



Epi-myocardium 



Neural groove 



Primitive streak 

 Amnion 



Hind-gut 



Exocoelom 



Omphalomesenteric artery 

 Epi-myocardium -^ u 



Fig ^, -Sections transverse to neural groove of 8 day i hour. 7 somite embryo. 

 .^1 except E are from the embryo shown in figure 22. The location of each section 

 is indicated on the key diagram. (X90.) 



