ON THE SUPRARENAL BODIES OP VERTEBRATA. 141 
vessels (diagrammetrically indicated by shading). The epithe- 
lium of the glomerulus is everywhere, except on its inner side, 
formed of a single layer of cells, which are much flatter than 
in the preceding stage, but on the inner side the cells pass, 
as before, without any definite line of demarcation, into the 
suprarenal blastema, which is still composed of a compact mass 
of polygonal cells, without any distinction being visible between 
the part which is going to form suprarenal body and that 
which is going to form a seminiferous tubule. In this section 
the distinction between the endothelial cells of the various 
blood-vessels and the tissues surrounding them is even better 
marked than in the one last described. 
The appearances which I have attempted to describe are seen 
first in the more anterior, then in the hinder glomeruli of all 
that region of the mesonephros which is coextensive with the 
generative ridge, and in one or two glomeruli in front of it. 
The blastema which I have described grows, in the suc- 
ceeding stages, in two directions : dorsalwards between the 
cardinal vein (or vena cava) and the tubules of the mesone- 
phros, and ventralwards into the prominence of the Wolffian 
ridge. In such a section as that shown in fig. 3, for example, 
which is taken from the posterior part of the mesonephros of 
an embryo of 8 mm., two distinct regions may now be distin- 
guished, a region (s. r. b.) dorsal to the point of origin from 
the glomerulus, the cells composing which will go to form the 
suprarenal, and a region ( s . str .) going from the glomerulus 
ventralwards into the generative ridge, which is the rudiment 
of the testicular network. No histological difference can as 
yet be detected between the one region and the other, the 
whole blastema being composed of a mass of polygonal cells 
with rounded nuclei, the characters of which are everywhere 
identical. 
In an embryo of 10 mm. (figs. 4 and 5), a slight dis- 
tinction between the two parts is for the first time apparent, 
though the histological characters of adult suprarenal cells are 
not acquired for some time. Of the two sections figured, that 
shown in fig. 4 is taken in front of the Wolffian ridge; in it, 
