184 W. F. B. WELDON. 



therefore, the blastema attached to the glomerulus gives rise 

 ouly to suprarenal tissue. For this figure, I have purposely 

 chosen a section in which the contact between the suprarenal 

 rudiment and endothelium of the vena cava was as close and 

 as extensive as possible, in order to show the distinctness 

 which, in spite of their close apposition, exists between the two 

 structures, and to contrast once more this distinctness of the 

 vena cava endothelium with the irregular way in which the 

 cells of the glomerulus wall are merged in the blastema. 

 This section is also interesting from another point of view. 

 One of the arguments used by Dr. Braun, in order to disprove 

 the existence of any real connection between the rudiment of 

 the testicular network and that of the suprarenal, is that the 

 segmental rudiments of the former structures are well developed 

 before the appearance of any suprarenal tissue at all. Dr. 

 Braun believes that the whole of the outgrowth from each 

 glomerulus becomes converted into a seminiferous tubule. 

 But if this be so, what can be the function of such an outgrowth 

 in front of the testicular region ? 



In fig. 5 is seen a section through the beginning of the 

 generative ridge : the suprarenal and seminiferous rudiments 

 are still continuous, but the one is a little more deeply stained, 

 and its component cells are a little smaller than the other. As 

 before, the endothelium of the surrounding blood-vessels forms 

 a distinct layer over the blastema, the cells of which are quite 

 sharply defined and clearly recognisable. 



The upward growth of the suprarenal rudiment, already 

 well marked in fig. 5, is still better seen in fig. 6, from the 

 middle of the trunk of an embryo of 13 mm. — almost the 

 oldest in which a connection between suprarenal and semi- 

 niferous tubules can be seen. In an embryo of 18 mm. 

 (fig. 7), the separation has already taken place, and the 

 suprarenal is cut ofi' by blood-vessels from all adjacent struc- 

 tures, though it remains now, as always before, perfectly 

 distinct from the endothelium of the vessels themselves. 

 This stage is only very slightly younger than the youngest 

 figured by Braun, as fig. 4, PI. I. of his paper shows; the 



