Development and Shape of Uriniferoiis Tubules 



embryo as in those of the cat and ral)l)it; they are, however, of similar 

 character and of sufficient degree to merit recognition. 



In Fig. 17, are represented three stages in the development of urinifer- 

 ous tubules as observed in the pig embryo. My observations on the 



A 



B 



dc-i 



m- I 



:-^pc • 



l-d 



■m 



Fig. 17. Three uriniferous tubules from kidneys of pig embryos. X 133. 

 A and C, from embryo of 2.8 cm. length (No. 8). The latter is representative 

 of the first generation of tubules, situated nearest the pelvis and is shown from 

 the Malpighian corpuscle to the first coil of the distal convoluted portion; the 

 former represents a much less developed tubule, one situated nearer the 

 periphery of the kidney; B, one of the most fully developed tubules from the 

 kidney of an embryo of 2.4 cm. length, vi, Malpighian corpuscle; j)c, 

 proximal convoluted portion; dc, distal convoluted portion; I, anlage of loop 

 of Henle; dl, of descending limb; al, of ascending limb; d, collecting tubule. 



development of uriniferous tubules in pig embryos are not as yet complete, 

 owing to the lack of suitable material showing the older stages of develop- 

 ment. They have for this reason not received more than casual mention 

 in the preceding pages. A fuller treatment is reserved for another 

 contribution, in which the development of the collecting tubules, more 



