130 MARION HINES 
the paraphyseal arch is a definite dorsal protrusion of the roof 
plate just anterior to the velum transversum. The tissue_con- 
tiguous to it is convex lateralward, the first indication of the 
invagination of the lateral choroid fissure. In all the rest of 
the series, the plexus exists as described for man by Bailey 
(16a), namely, the choroid plexus of the lateral ventricle con- 
sists of two divisions, an anterior, whose lateral taenia is that of 
the fornix and whose medial is the lateral limb of the paraphyseal 
Fig. 15 Median sagittal view of the forebrain of H 178. a 19.1-mm. human 
embryo, belonging to the Chicago collection. > 163. 
arch, and a posterior, whose lateral taenia is the same as that of 
the anterior division, but whose medial taenia is the telencephalic 
limb of the di-telencephalic groove, the taenia chorioidea. In 
these older embryos the hippocampus forms a complete crescent 
dorsal and lateral to the plexus. In all stages the primordial 
hippocampus precedes the choroid plexus as the hemisphere grows 
caudally. 
Bailey (16a, fig. 15, a. c. p.) has suggested that the growth 
of the posterior limb of the lateral choroid plexus is a simple 
