THE EMBRYOLOGY OF THE HONEY BEE 225 



-Meso 



-AMR 

 (Mint) 



W* 



>.<« 



tr^ 



PMR 

 (Mint) 



Meso--'' 



Meso 



Fig. 88. Anterior (A) and posterior (B) ends of a median sagittal 

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

 and posterior (PMR) mesenteron rudiments, which have now united along 

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

 well developed, while the protodaeal invagination (Proc) is indicated by 

 a slight depression, x 243. 



present (Fig. 89A). The next and final step, which takes place 

 about the time of hatching, involves the actual invagination of the 

 inner end of the stomodaeum — now the oesophagus — into the 

 mid-intestine, and the rupture of the closing membrane. This 

 rupture seems to be caused mechanically by pressure of the inva- 



