THE NECTURUS 67 



supplied with a chorioid plexus. The borders of this ven- 

 tricle form the fossa rhomboidalis of the dorsal side of 

 the brain. 



The crura cerebri are formed by the widening out of this 

 ventricle at the anterior end of the medulla, thus forcing 

 the fibers that were more dorsal on the cord, to bend 

 sharply to one side at this point. 



Drawing 25. Make a drawing of this sagittal section X 6. 



The flexures are not very evident in the adult brain of 

 Necturus. 



