fclDNEY IN RELATION TO WOLFFIAN BODY IN THE CHICK. /D 



15 to 17) a blastema of cells is still present, precisely 

 similar in its appearance and position with regard to the 

 Wolffian duct to the Wolffian blastema seen anteriorly at 

 earlier stages, and to the blastema seen in the same region 

 at later stages (fig. 12). And this can be traced back to the 

 opening of the Wolffian duct into the cloaca (fig. 17). 



To this blastema of cells I have given the name kidney 

 blastema; it is at this stage perfectly continuous anteriorly 

 with the hinder Wolffian tubules, the junction between the 

 two lying in one of the two sections intervening between 

 figs. 14 and 15. I ought rather to say the line of future 

 separation, for so far they have been always continuous, 

 having developed so. The continuity between the kidney 

 blastema {/cb) and the hinder part of the Wolffian body 

 may be seen in fig. 21, which is taken from a chick of nearly 

 the same age as that from which figs. 13 — 17 were. 



In this figure the section has passed through the hind end 

 of the Wolffian duct and through the kidney blastema, and 

 has just shaved the hinder end of the Wolffian body, in conse- 

 quence of which the hinder Wolffian tubules are only indis- 

 tinctly visible. 



The next change to notice is caused by the appearance of 

 the ureter. It arises as a growth forward from the dorsal 

 border of the enlarged end of the Wolffian duct. This has 

 been generally recognised since Kupff'er's^ account. The dila- 

 tation of the hind end of the Wolffian duct occurs in a very 

 slightly later embryo than that from which fig. 21 was taken. 



The kidney blastema is now found not ventrally close to 

 the body-cavity, but lies dorsal to its former position, just 

 internal to the dorsal extremity of the dilated Wolffian duct 

 (fig. 20). From this dilatation there grows forward a duct, 

 the ureter (fig. 19), on the inner side of which lies the kidney 

 blastema. 



The ureter, at this stage, has not a very great extent, and 

 is only seen for a few more sections ; in fig. 18, still behind 

 the Wolffian body, the ureter is not visible ; but the kidney 

 blastema occupies a dorsal position, as it did in the posterior 

 section in which the ureter was present (fig. 19). 



In tracing it forward it gradually descends and becomes 

 continuous with the hind end of the Wolffian body. 



In yet older embryos, in which the ureter is more developed 

 and overlaps the hind end of the Wolffian body, the kidney 

 blastema has quite broken off" from the Wolffian body, and 

 invests the anterior end of the ureter, so that in a series of 

 traiisverse sections through a chick at this age we should see 

 1 ' Arch. f. M. Anat./ Bd. 2. 



