John Warren . idl 
hemispheres, L. Plz., and the lateral ventricles, L. V. It shows clearly 
how the plexuses of the hemispheres arise from the telencephalic plexus 
and pass at first outward and then forward through the foramina of 
Munro towards the cephalic extremity of the lateral ventricles. 
Figs 15 is a high power drawing of Fig. 11, magnified 150 diams. 
The wall of the paraphysis consists of a single layer of cells with large 
oval nuclei, and these cells are continuous with the cells covering the 
choroid plexuses, but the latter are flatter and form a thinner layer. On 
either side of the paraphysis two large vessels are seen, ves., the epithelial 
cells of which lie directly against the wall of the paraphysis. The little 
tubules seem to be forcing their way into these vessels, which are branches 
of the vessels seen in Fig. 6 and Fig. 10. The vessels also pass down into 
the choroid plexuses. Fig. 16 is a section of an embryo of 31.4 mm. 
“Oy 
O.Ch. 
Fic. 16. Embryo of 31.4 mm. Harvard Embryological Collection, Sagittal 
Series, No. 537, Sections 119-122, * 63 diams. 
The general arrangement is practically the same as in Fig. 11, except that 
all the parts have progressed somewhat in their development. The distal 
end of the paraphysis has begun to grow distinctly more cephalad, and the 
whole structure is much larger than at 26 mm. The choroid plexuses are 
more extensive, and from the diencephalic plexus a prolongation is ex- 
tending downwards towards the telencephalic plexus. This latter has 
pretty well filled up the depths of the third ventricle, and from it pro- 
longations dip down into the recesses in the floor of the fore brain. The 
two commissures are practically the same as they were at 26 mm., and 
