Stom 



Meso. 



A 



AMR 



-PMR 



PMR 



Meso 



Fig. 87. Anterior (A) and posterior (B) ends of a median sagittal 

 section through an embryo, Stage VIII, showing the anterior (AMR) 

 and posterior (PAIR) mesenteron rudiments, which are about to unite on 

 the dorsal surface of the egg. The stomodaeal invagination (Stom) is 

 just appearing. The relation of this to the anterior mesenteron rudiment 

 is clearly shown, x 243. 



