DEVELOPMENT OF THE CHOROID PLEXUS 105 



chorioidea, or in other words, along the hne of attachment of 

 the plexus to the medial hemisphere wall. If, therefore, we 

 wish to follow the taenia fornicis et thalami in the embryo CR, 

 we must follow the Hne marked with crosses in figures 16 and 17 

 along the wall of the diencephalon (figs. 1() and 17, t.t.), across 

 the velum transversum, and then between the area chorioidea 

 posterior and area chorioidea anterior above and lateral to the 

 fissura chorioidea (figs. 1() and 17, t.f.). 



It will be seen (fig. 17) that the area chorioidea anterior hes 

 entirely anterior to the velum transversum. The lateral choroid 

 plexus never approaches the mid-line except along the sides 

 of the paraphysal arch, anterior to the velum transversum. 

 The area chorioidea posterior has relations entirely analogous with 

 its relations in figure 15, except for its change of face. It lies 

 between the hippocampus and the di-telencephalic groove, and 

 adjoins the posterior end of the taenia fornicis on the upper 

 side, which in figure 15, was the lower side of the taenia. 



This stage in the process bears a close resemblance to the 

 condition in the brain of Phitydactylus mauritanicus, as de- 

 scribed by Tandler and Kantor ('07). Concerning the develop- 

 ment of the structures in the region of the foramen of Monro, 

 they write (italics mine) : 



Die zwischoii don bcidcn Foramina Monroi gclegene Deckc dcs 

 Ventriculus impar [telencephalon niediuni] ist rein epithclialer Natur 

 and grenzf sicli laterahi'drts durch je cine dcutliche Furche Sulais tcgmenli 

 ah. 



The lateral edge of this sulcus tegmenti is the taenia fornicis. 



Die Fissura chorioidea, wclche von hinten her den Rauni des Fora- 

 men Monroi einengt, entwickclt sick, wie die Durchsichi dcr Serielehrt. 

 derart, dass sie im vordercn Ahschnitt aus dem Sulcus tegmenti selbst. 

 hinten aber oberhalb diescr Furche entsteht, und hier die mediale 

 Hemispharcn wand einschneidet. 



Der Plexus chorioideus des Ventriculus lateralis stijlpt niimlich 

 nur ein ganz kurzes Stiick der Hirnwand ein. Die Einstiilpungsstelle 

 selbst, liegt wie man inn Stadium V zeigen kann, gerade dort, ico das 

 hinfere Ende des Sulcus tegmenti die Decke des Telencephalon impar von 

 der medialen H emisphdrenwand absetzt. 



