G. Carl lluber 7 



sections having a tliickncss of 10 to 20 /x were not suitable for interpreting 

 the early stages of kidney development, as in some sections fields were 

 found which might be used respectively for demonstrating either a con- 

 tinuous or discontinuous origin of the coiled uriniferous tubules. It was 

 further hoped that a solution of the question might be obtained by inaking 

 free use of reconstruction methods, especially of the Born wax-plate 

 method. Tlie wax-plate method of reconstruction had previously been 

 used in the study of the development of the kidney by Chievitz. He gives 

 three figures, which are, however, somewhat difficult to interpret, owing to 

 the fact tliat the models were not completed by smoothing over the 

 irregularities which always result when the cut-out portions are placed 

 together. Since my own investigation was begun and in part completed, 

 there have appeared three contributions based in part or as a whole on 

 data gained by reconstructions. Mention has been made of the work of 

 Schreiner, who, however, studied, among other questions, only the anlage 

 of the coiled tubules and of this portion of his work he gives no recon- 

 structions. Haugh's reconstructions are confined almost wholly to such 

 of the pelvis and straight collecting tubules of kidneys of relatively young 

 human embryos. It is rather to be regretted that Haugh did not 

 devote more time to the finishing of his wax models, which would have 

 enabled him to give clearer illustrations of the models made, than 

 accompanying his otherwise excellent article. The most recent con- 

 tribution to this subject, that of Stoerk, is based largely on results obtained 

 by means of wax-plate reconstructions, the value of which method he 

 clearly recognizes. The contributions of Schreiner, Haugh, and Stoerk 

 which, as stated, have appeared since my own work was in progress, have 

 been of material assistance to me in formulating my own views. They 

 do not, however, as appears to me, make superfluous the publication of my 

 own results. These are confirmatory, as will appear, of that portion of 

 Schreiner's work which deals with the anlage of the metanephros and 

 its tubules; Haugh touches only incidentally on the development of the 

 coiled uriniferous tubules; and finally my own observations have led me to 

 conclusions which differ materially in a number of particulars from those 

 reached by Stoerk. 



The investigation, as projected, included not only a study of the 

 anlage of the uriniferous tubules and their mode of development, but also 

 a study of the form of the more fully developed uriniferous tubule, if 

 possible by means of wax-plate reconstruction. That this seemed desirable, 

 requires, I believe, no argument. A portion of the results here given were 

 presented at the December meeting of the Association of American 



