54 



Development and Sliape of Uriniferoiis Tubules 



surfaees recognized by their shading represent the origin of two branches, 

 similar to those reproduced. The collecting tubules are at this stage 

 of development relatively large with wide lumen. The one here shown 



Fig. 10. A model of a primary collecting tubule, cut just above its origin 

 from the pelvis of the kidney, showing six successive dichotomous divisions. 

 Only one of the four main branches of the second generation of branches is 

 here shown in full, together with renal vesicles, tubular anlagen and urini- 

 ferous tubules developing in connection with this branch. From the kidney 

 of a human embryo (No. 11). measuring 6.5 cm. x 133. 



presents four successive dichotomous divisions, the end-branches showing 

 ampullar enlargements. The pelvis of this kidney and the collecting 

 tubules here shown are lined by a single layer of columnar cells. The 

 figure shows further three renal vesicles, rv, five tubular anlagen in the 

 S-stage, seen from different aspects and showing different degrees of 



