188 W. P. R. WELDON. 



selves to tlie epithelium of the glomeruli, so as to appear as ia 

 fig. 18. In this figure the epithelium of the glomerulus is seen 

 to be distinct from the suprarenal for a short distance ; but in 

 a part of the section I was unable, after a tolerably careful 

 examination, to convince myself of the existence of any distinct 

 layer of epithelial cells separating the cavity of the glomerulus 

 from the adjacent blastema. 



Such a section as that shown in fig. 18 may be seen in almost 

 any glomerulus in the region of the suprarenal during the 

 seventh day. On the eighth day the appearance of the blas- 

 tema changes. While still retaining its connection with the 

 glomeruli (fig. 19) it has increased considerably in size, audits 

 component cells have acquired most of the histological charac- 

 ters which they present in the adult. The individual cells are 

 large, polygonal, and distinctly marked off one from the other ; 

 their protoplasm, which does not stain very readily with car- 

 mine or haematoxylin, is clear or very finely granular, and their 

 nuclei are clear, oval, or elliptical, with well-defined contours 

 and a number of coarse granules in their interior. The most 

 characteristic feature in the blastema of this age is, however, 

 the definite arrangement of the cells into columns, giving them, 

 more than at any earlier stage, the appearance of the cortical 

 substance of an adult suprarenal. 



I have already said that the blastema during the eighth day 

 remains attached to the glomeruli ; such appearances as those 

 seen at x in fig. 19, which are very frequent, tempt one 

 strongly to believe that at this time the number of the cells 

 composing it may be added to by proliferation from the glome- 

 rulus epithelium ; but I have not been able to satisfy myself 

 that this is the case. 



From this time the changes in the cortical blastema, so far 

 as I have followed them, do not differ in any important parti- 

 culars from those described by Braun in Lacerta muralis. 



A noticeable feature throughout the whole of the early 

 history of the organ under consideration in the chick, is the 

 very distinct separation between the cortical blastema and the 

 blood-vessels, the original blastema- cells being at a great 



