ile MARION HINES 
terior limb, and the less extensive, the less that portion will be 
developed. Bailey (16b) says, discussing the morphogenesis 
of the choroid plexus: 
| Figs.33| [54 35) | cs leres z 
Par ary ee 
Telch.tel med. x 
A.int. xX 
SV Dienr pl 
Undif fas.den./ Prim hip 
/ 
Pl.ch. 
vent lat 
Sul.vent. 
Sos oe / Hf 
a 
BEN STA ih sul dors. 
Cul wall of dien. 
Lamferm/ 
Rec.pre op SA 
Op.c. es , 
= Rec. inf 
l iI ellie cS al af Post. | hyp. 
st GP GPS | Gy a a} 
# 86 BO ® r * 
Fig. 17 This is an outline sketch of the brain of a 20-mm. embryo, no. 460, 
belonging to the Mall Collection. The area indicated by stippling corresponds 
to the extent of the fissura hippocampi. The planes of section of figures 33 to 
37 are indicated. 
In all forms below Chelonia, the lateral telencephalic plexus develops 
in what I have called elsewhere (Bailey, ’16a) the anterior lateral 
telencephalic chorioidal area, in the roof plate of the telencephalon 
between the paraphysis and the taenia fornicis of the medial hemisphere 
wall. With Chelonia comes a change. The lateral plexus arises in 
the anterior area chorioidea lateralis telencephali, as has been previously 
described, but in its later development crosses the taenia fornicis and 
invaginates also the posterior area chorioidea lateralis telencephali in 
the medial hemisphere wall. . . . . This involvement of the 
medial hemisphere comes more and more to predominate in the develop- 
