MORPHOGEXESIS OF THE CHOROID PLEXUSES 517 



Of the forms between Insectivora and Man nothing of value is 

 known. Ziehen ('06) shows sections of the lateral telencephalic 

 plexus of Tarsius spectrum, a prosimian, but not in the proper 

 plane to be of value, and again describes the anterior pouch of 

 the diencephalic roof as the paraphs-sis. 



Sehr beachtenswert ist auch, dass unmittelbar hinter der Fossa prae- 

 diencephalica die epitheliale Dccke des Z\\-ischenhirns sich zu einer 

 stulen Falte, welche an die Parapliyse erinnert, erliebt und dass erst 

 einige Schnitte weiter occipitahviirts diese steile Falte durch den nicdiane 

 Plexus des 3. Ventrikels eingestiilpt wird. 



In an earlier paper, the author (Bailey, '15) called attention 

 to the true homologue of the paraphysis in the human embryo 

 and insisted upon its position in the telencephahc roof plate just 

 anterior to the velum transversum. Previously, Streeter ('12), 

 Francotte ('94) and D'Erchia ('90) had written of the paraphysis 

 in the human embryo. Streeter homologizes the anterior pouch 

 of the diencephalic roof with the paraj^hysis, and from a com- 

 parison of Francotte 's figures witli sections of embryos of approxi- 

 mately the same stage, I am convinced that he mistook the same 

 structure for the paraphysis. D'Erchia shows a section from a 

 30 mm. human embryo in which he labels a structure 'paraphy- 

 sis' which seems to me to be merely an oblique section of the 

 lateral telencephalic i)lexus. 



In his model of a LS.O nmi. human embryo. His shows clearly 

 the lateral telencephalic plexus coming off lateral to the paraphy- 

 sal arch, but his statement ('04) of the origin takes no account 

 of this fact. "Sein deni Thalanms angehefteter Randstreifen 

 bleibt epend\^nal und in ihm bildet sich die Fissura chorioidea, 

 von der aus die Epithelfaltungcn des Corpus chorioideum in den 

 Seitenventrikel sich einstiilpen." 



Hochstetter ('13) in his account of the development of the 

 lateral telencephalic plexus in the human embryo shows one 

 figure (fig. 6) of a section through the plexus which passes also 

 through the telencephahc roof plate, but his description contains 

 nothing concerning the origin of this part of the plexus. 



D'Erchia ('96) considers the lateral telencephalic plexus to be 

 derived from the \'elum transversum: ''Per questa parte volga 



