DEVELOPMENT OF THE CHOROID PLEXUS 107 



cis as far as the area chorioidea posterior, then along the upper 

 margin of the area chorioidea posterior (anterior margin in fig. 15) 

 called also taenia fornicis in adult anatomy, around its posterior 

 extremity (lower extremity in fig. 15), and back along its lower 

 margin (posterior margin in fig. 15) called also taenia chorioidea, 

 to the lateral end of the velum transversum where we finally 

 reach the taenia thalami. 



It thus appears that the portion of the taenia fornicis of human 

 anatomy which hes adjacent to the pars posterior plexus cho- 

 rioidei ventriculi lateralis is not homologous to the taenia fornicis 

 in Anura and would better be called taenia suprachorioidea, 

 and the taenia chorioidea correspondingly termed taenia infra- 

 chorioidea. The illustrations have been labeled in accordance 

 with established usage. To place them in accord with the 

 foregoing conclusions, in figures 1, 11, 12, 18, 24 and 26 taenia 

 fornicis should be changed to taenia suprachorioidea, and taenia 

 chorioidea to taenia infrachorioidea. 



In later stages the taeniae infra- et suprachorioiilea become 

 approximated closely as is found in the 2S mm. embrj'o and in 

 the 32 mm. embrj^o, and the fissura chorioidea is reduced to a 

 narrow slit, its axis in the plexus of the 19 mm. embryo, lying 

 probably along the dotted line in figure 19. 



In the 28 mm. embryo and the 32 mm. embryo, it is impos- 

 sible to distinguish the dividing lino between the pars anterior 

 and the pars posterior of the lateral choroid plexus, and the taenia 

 fornicis in its restricted sense is relatively of very short length. 



i. Sulcus limitans. The sulcus limitans is lost in a deep re- 

 cess between the corpus striatum and hypothalamus. This 

 recess has disappeared by fusion of its walls in the 32 mm. em- 

 bryo. If the sections of the 19 mm. embryo be followed, the 

 beginning of this process can be readily seen (fig. 2). 



j. Corpus striatum. There is nothing extraordinary about the 

 corpus striatum in either embryo. The approximation of the 

 thalamus and corpus striatum in the foramen interventriculare 

 (fig. 22) is of interest when one remembers Goldstein's work. 

 Of course, the entire connection between the thalamus and 



