G. Carl Hiiber ' 35 



of this tubular aiilage shown in D of Fig. 3. In the reconstruction it 

 will be seen that what appears in section as the lower S-curve represents 

 in reality a shallow bowl, the edges of the saucer-shaped structure recog- 

 nized in the former stage and figure having grown upward, thus deep- 

 ening the concavity; also the space which separates this part of the 

 anlage from the lower end of the upper S-curve and S-middle piece has 

 increased somewhat and is now occupied by a vascularized mesenchyme, 

 the section reproduced showing two capillaries, the one cut cross-wise, 

 the other seen in longitudinal section. The mesenchyme contained 

 within the concavity of the lower S-curve has long been recognized as 

 the anlage of a glomerulus, this portion of the tubular anlage, as may 

 be stated now, forming Bowman's capsule. My own observations lead 

 me to think that the first capillary loop found within the mesenchyme 

 occupying the concavity of the lower S-curve of a tubular anlage grows 

 into this from without, as I have generally been able to trace a connection 

 between it and the capillaries outside of the cleft occupied by the mesen- 

 chyme. To give definite answer to this question, however, it would be 

 necessary to confirm the above statement on injected preparations, but 

 the fresh material of the proper stage of development, obtained during 

 the course of this investigation, was too limited to attempt this. This 

 question has received only incidental mention by other investigators ; of 

 the more recent of these we may mention Schreiner, Avho simply states 

 that " into the cleft there grow from without connective tissue and 

 vessels,'' and Stoerk, who, in speaking of the development of the S-shaped 

 stage of the tubular anlage, states that " there is formed between the 

 upper curve and the middle piece on the one side and the concavity of the 

 lower curve on the other side a dowaiward curving cleft, which takes up 

 vascularized interstitial tissue, from which later the glomerulus is de- 

 veloped." Herring, on the other hand, states that when the S-shaped 

 tubule is formed, the space between the lower and the middle limb is 

 occupied by some connective tissue cells; they are few in number and 

 resemble the other cells which are found in the matrix of the cortex. He 

 further states that " From these cells I believe the capillaries of the 

 glomerulus are formed in siiu and not as an ingrowth." 



The S-shaped stage in the development of the urinlferous tubule, especially charac- 

 teristic when seen in sagittal sections, has long been recognized and was first correctly 

 described by Toldt and is clearly brought out in Golgi's semidiagrammatic figures of 

 developing uriniferous tulnilcs of mammals. The series of developmental stages leading 

 to the formation of the S-shaped tubular anlage have, I believe, been correctly described 

 only by Schreiner, whose account my own observations, as given hei-e, in the main 

 confirmed. 



Ribbert gives in a series of semidiagrammatic figures (Pig. 3 of his article) his 

 view of the development of the S-shaped stage of the tubular anlagen. By means 

 of these fiirurcs. he aims to show that the lower portion of the cell-mass from which 

 a tubule is developed, In its growth turns sharply upward, toward the periphery of the 

 kidney. In this way. a cleft is formed between the elongation and the cell-mass 

 from "which it develops ; the latter now makes union with the collecting tubule, the 



