The Brah, 



291 



The Brain. 

 The brain commences to form and is recognizable before the 

 neural canal has been completed. It consists at first chiefly of a 

 senesof vesicles which are known as the fore-brain, mid-brain 

 and hmd-brain. The anterior cerebral vesicle, or fore-brain, gives 

 rise very early in its development to the optic vesicles, as lateral 

 outgrowths, which are ultimately converted into the essential 

 parts of the eye. 



Normally, there are two of these outgrowths, which, under 

 aberration m development, may fuse or grow out as single pro- 

 jections on the median line, to constitute the one-eyed monster 



MP 



SM 



IM 



Fig. 29. Skui,!, of Cyclops. Foai,. 

 Oc, Occiput. O, Single orbital cavity. 

 MP, Coronoid process of inferior maxilla. 

 SM, Superior grinders. 



SI, Superior incisors fused into a single oro-an. 

 IM, Inferior grinders. T, Tongue. 

 II, Inferior incisors. 



