G. Carl Hiiber . 57 



collecting tubules. The one tubule of each model having a different 

 attachment is attached to the collecting tubule; in the model showing the 

 younger stage of development, in the region of the second division, in the 

 other model, in the region of the third division. I have observed this 

 condition onl}' in the human embryos. In the kidney of the cat and 

 rabbit of about the same stage of development, as shown in these models, 

 all the uriniferous tubules and tubular anlagen are attached to the 

 ampullar enlargements of the end branches of the collecting tubules. 

 Hamburger, who has made observations on the mode of attachment of 

 the "coiled uriniferous tubule" to the "straight collecting tubule" on 

 certain animals, has reached the following conclusions: He speaks of 

 the branches of the straight collecting tubules which result from the last 

 division of these (as seen in the fully developed kidney) as the " terminal 

 collecting tubules" and finds that in the beef and the mouse and 

 generally also in the rat these terminal collecting tubules take up the 

 ends of the coiled uriniferous tubules and only seldom (in the rat) do 

 these terminate in the straight collecting tubules proximal to the terminal 

 branches, while in the pig a greater number of the coiled uriniferous 

 tubules end in the straight collecting tubules and that these further 

 form arcades, with convexity upwards, which also serve for the insertion 

 ^of the coiled tubules. The fact that at a relatively early stage in the 

 development of the human kidney certain uriniferous tubules end in the 

 collecting tubules proximal to their terminal branches indicates that this 

 mode of termination obtains in post-uterine life, while the fact that in 

 cat and rabbit embryos of about 2.5 cm. length, all the tubules end in 

 the terminal branches would go to show that even in the fully developed 

 kidneys of these animals, the great majority of the uriniferous tubules 

 end in this way. Positive statements concerning this point I am at 

 present unable to make, as I have not reconstructed collecting tubules 

 throughout their whole extent for stages older than given in Fig. 10. 



Figure 9 will also serve to show that the collecting tubules in their 

 growth and successive divisions resulting in the formation of new 

 branches, do not in these successive divisions divide in the same plane, 

 but with some degree of regularity in alternate planes. The configu- 

 ration resulting from the last two divisions of a collecting tubule during 

 the time when these form new branches, would resemble two Y^s the stems 

 of which are joined to form a single stem, the four arms of which project 

 into four quadrants of a circle. The diagram given in Fig. 12 may 

 serve to make this clear. Uriniferous tubules develop in connection 

 with each of the four end branches thus formed. In each of the two 

 tubules developing in connection with the two anterior end branches, as 



