ON THE SUPRARENAL BODIES OP VERTEBRATA. 181 



been led to believe that the blastema of Gottschau, Mitsu- 

 kuri, and others arises as a series of (segmental?) outgrowths 

 from the peritone^im, 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 siiprarenal 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 WolflSan 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 

 invaeinated ; and I may here call attention to the manner in 

 which in lizards at least, the invagination seems to take place 



