502 Journal of Comparative Neurology and Psychology. 



In this way appears the chorioid fissure whose further history need 

 not be traced. Near the median plane the plexus appears as a fold 

 projecting into the interventricular foramen and separated from the 



Fig, 40. A parasagittal section from the embryo diuwu in Fig. 39. 



C.S 



Fig. 41. Pig embryo, 15 mm. Three sections from a frontal series showing 

 the relations of the chorioid fissure and plexus to the lateral hemisphere 

 and the thalamus. The section to the left is the most ventral, that to the 

 right the most dorsal. 



velum transversum by the paraphysal arch. From this stage on the 

 plexus grows rapidly and becomes very large and in the median 

 region both the velum and the paraphysal arch become involved in 



