^] 



THE CRANIAL FLEXURE. 



333 



dfp. splanchuic mesoblast; ph. pericardial section of body- 

 cavity ; ahh. muscular wall of heart ; ihh. epithelioid layer of 

 heart ; mes. lateral undivided mesoblast ; sw. fold of hypo- 

 blast which will form the ventral wall of the pharynx ; &r. 



commencing throat. 



The later stages in the development proceed in the 

 main in the same manner as in the Bird. The cranial 

 'flexure soon becomes very marked, the mid-brain form- 

 ing the end of the long axis of the embryo (Fig. 108). 

 The sense organs have the usual development. Under 

 the fore-brain appears an epiblastic involution giving 



Fig. 108. 



TJiS 



md 



am 



Advanced Embryo of a Rabbit (about Twelve Days)\ 



wh. mid-brain ; th. thalamencephalon ; ce. cerebral hemisphere ; 

 op. eye ; iv.v. fourth ventricle ; mx. maxillary process ; md. 

 mandibular arch ; hy. hyoid arch ; fl. fore-limb ; Id. hind- 

 limb ; um. umbilical stalk. 



^ This figure was drawn by Mr Weldon. 



