DEVELOPMENT OF THE CHOROID PLEXUS 



9: 



The commissura superior is very readily identified (fig. 22, 

 com.s.). 



.The epiphyseal evagination (fig. 22, e.e.) is, in all essential 

 respects, identical with that of the 28 mm. embrj'o. 



The lateral choroid plexus (fig. 12, p.c.v.l.) also resembles 

 that of the 28 mm. embryo. The posterior portion is more swol- 

 len, resembhng more nearly the anterior part. The ependyma 



13 



14 



•pl.al. 



(liurii of the 



Fin. 13 Section tliiouKli tin- roof i)latc of tlic tele 

 32 mm. embryo, H 41. X 50. Slide 32, Sect. 4. 



Fig. 14 Section through the roof plate of the telenrephalon medium of tiie 

 32 mm. embryo, H 41. X Ti. Slide 32, Sect. 4. 



is almost entirely a single layer of cells except at the extreme 

 caudal end of the plexus. The plexus extends through 4.44 

 mm.; the ventricle through 7.2 mm. The plexus extends 1.6 

 ♦mm. anterior to its most anterior point of attachment. 



On the ventricular surface we find again that the corpus 

 striatum exhibits three roots at its anterior end (fig. 24, c.s.). 

 The most medial root, in the lateral wall of the third ventricle, 

 is narrow, lies immediately back of the lamina terminalis, and 



THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 26, N< 



