ON THE SUPRARENAL BODIES OF VERTEBRATA. 139 
been led to believe that the blastema of Gottschau, Mitsu- 
kuri, and others arises as a series of (segmental?) outgrowths 
from the peritoneum, in the angle between it and the root of the 
mesentery and the peritoneum. As, however, very few figures 
are given with this paper it is not easy to form an idea of the 
exact nature of the events described. 
This state of things led me to believe that it might be 
worth while to examine carefully embryos younger than those 
used by any previous observers, and so to trace the earlier 
history of the cortical blastema. This I have been able to do, 
during the summer of the present year, in the chick, in 
Lacerta muralis, and in Pristiurus. As my observations 
are most complete in the case of Lacerta, I begin with an 
account of the development in that type. In order fully to 
understand the development of the suprarenal body, it will be 
necessary to follow the development of the glomeruli of the 
mesonephros, which has been described by Braun (loc. cit.) 
After the formation of the segmental vesicles and Wolffian 
duct each segmental vesicle gives off from its outer margin a 
solid column of cells, which joins the Wolffian duct, and soon 
acquires the (/) shape characteristic of the young segmental 
tubes in so many Vertebrates. After this cord of cells has 
united with the Wolffian duct, the lumen of the segmental 
vesicle extends into it, and it takes on all the characters of 
a segmental tubule. After this has happened, one wall of the 
persisting segmental vesicle becomes pushed in by a plexus of 
blood-vessels, and forms a glomerulus. 
But while the wall of the glomerulus is being thus invagi- 
nated, a proliferation of the cells composing it occurs at the 
side opposite to the point of attachment of the segmental tube, 
that is, on the inner margin of the glomerulus. 
In fig. 1, 1 have attempted to represent the condition of things 
in one of the anterior glomeruli of an embryo with about 
twenty protovertebrse. The section passes nearly through the 
centre of the glomerulus, which is seen to be only partially 
invaginated ; and I may here call attention to the manner in 
which, in lizards at least, the invagination seems to take place 
