X.] 



THE CRANIAL FLEXURE. 



333 



dfp. splanchmc mesoblast; ph,. pericardial section of body- 

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

 heart ; mM. lateral undivided mesoblast ; sm. fold of hypo- 

 blast which will form the ventral wall of the pharynx ; sr. 

 commencuig 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. 



mS 



m d 



urn 



Advanced Embryo op a Rabbit (about Twelve Days)'. 



rnb. mid-brain; th. thalamencophalon ; ce. cerebral hemisphere; 

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

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

 limb ; wm. umbilical stalk. 



1 This figure was drawn by Mr Weldon. 



