GS 



Development and Sliapc of TTriniferous Tubules 



letter a. belong to a tubule of tlie tvpe sbown in (' and 1) of the previous 

 figure; tubule h is the one shown in A of that figure. In the remainder of 

 the section may be seen renal vesicles and tubular anlagen in various stages 

 of development. This portion of the sections which constitutes the neogenic 

 and subneogenic zones, stains more deeply than the portion containing the 

 well developed proximal convoluted tubules; these, by reason of the fact 

 that they are lined by a differentiated epithelium (as previously de- 



a a 



Fig. 15. A portion of a cross section through the kidney of a rabbit embryo 

 of 3.5 cm. length (No. 8). x 100. a. sections of proximal convoluted portion 

 and Malpighian corpuscle of a uriniferous tubule representative of the first 

 formed tubules of this kidney; a', section of ascending limb of Henle's loop of 

 the same; &, tubule shown in A of Fig. 14, representative of a later generation 

 of tubules; ct. collecting tubule; c. capsule. 



scribed), the protoplasm of the cells of which stains faintly in eosin 

 and erythrosin, form a zone which stains less deeply than the more 

 peripheral portions containing the tubular anlagen with undifferentiated 

 epithelium of an embryonic character. In Fig. 16, are shown two urinif- 

 erous tubules, A. from the kidney of a cat embryo of 4 cm. length; B 

 from the kidney of a cat embryo of 6 cm. length ; Ijoth are representative 

 of types of tubules found nearest the pelvis of the respective kidney and 

 show more advanced stages of development than arc shown by tubules C 

 and D of Fig. 14. Tubule .4 measures 3.75 mm., of which 1.9 mm. 

 falls to the proximal convoluted portion, the entire* loop (ascending and 



