140 
W. F. B. WELDON. 
before the entrance of the blood-vessels, none of which are 
to be seen in the section figured. The epithelium is much 
more columnar than at a later stage, and is regularly one cell 
thick on the outer side, while on the side undergoing invagina- 
tion it is more or less regularly composed of two layers of cells ; 
but at every point except one the whole glomerulus is bounded 
by cells of a definitely epithelioid character, having no pro- 
cesses, and showing no indication whatever of any tendency to 
proliferation. At the inner margin, however, the case is 
different; here the limiting cells are irregular in shape, and 
can in no way be separated, by any sharp line of demarcation, 
from the cells forming the /^-shaped mass (s. r. b.), which is 
seen to be attached to the inner wall of the glomerulus. This 
mass gives rise both to the connecting tubules between testis 
and epididymis and to the cortical substance of the suprarenals. 
At present it is seen to extend for a short distance dorsal- 
wards, between the segmental tubule ( s . t.) and the vena cava 
(v. c.), and then to bend rather sharply ventralwards towards 
the generative ridge, the anterior end of which ( TV. r .) is seen 
in the section. As a contrast to the continuity between the 
cell mass in question and the cells bounding the cavity of the 
glomerulus I would especially call attention to the distinctness 
of the line of demarcation between it and the endothelium of 
the vena cava, at the point where the two are in contact — a 
distinctness which, persisting, as we shall see it to do, through 
all stages of the development of the suprarenal blastema, ren- 
ders it extremely difficult to believe that the endothelium is in 
a state of proliferation, or that there is any real connection 
between it and the suprarenal blastema. 
The small blood-vessel ( b . v.) which is seen in the figure 
is also perfectly sharply separated from the adjacent tissues. 
The section represented in fig. 2,» from an embryo about 
4‘5 mm. long, with twenty-four protovertebrse, shows a further 
advance in the development of the suprarenal blastema and its 
associated glomerulus. The section, which passes through the 
entrance of a segmental tube into the glomerulus, shows the 
completion of the invagination, and the entrance of blood- 
