KIDNEY IN RELATION TO WOLFFIAN BODY IN THE CHICK. 63 



Kupfter/ Bornhaupt,^ and Braun/ on the other hand,, 

 assert that the secretory tubules and Malpighian bodies are 

 formed independently of the ureter in the condensed meso- 

 blast tissue mentioned above, the outgrowths from the ureter 

 merely giving rise to the collecting tubules. 



1 shall return, when I have described the kidney develop- 

 ment in the chick, to a consideration and discussion of 

 the various hypotheses which have been held concerning the 

 Amniote kidney. 



Development of Wolffian hody. — The ages of the younger 

 embryos from which the sections figured in the accompany- 

 ing plates (VI and VII) were taken are indicated by 

 the number of protovertebrse. In the older embryos this 

 was not possible. In most cases the place in the body, 

 from which a section figured was taken, is indicated by the 

 number of the segment^ in which it occurred, counting 

 the first segment behind the auditory involutions as the 

 first. 



These determinations have been made with some care by 

 mounting all the sections in order, and then by observing the 

 protovertebrse, arranging them into groups corresponding to 

 each protovertebra, beginning the process always in front. 



The observations here recorded do not extend to any part 

 of the Wolffian body in front of the fourteenth segment, nor 

 to the development of the Wolffian duct. I have made 

 some observations on both these parts, but they are not yet 

 sufficiently complete to enable me to understand certain 

 remarkable appearances in their development. The Wolf- 

 fian body, like most other organs, develops first of all in 

 front and then gradually backwards, so that supposing the 

 development behind were the same as in front, the process 

 might be shown by a series of sections from a single chick 

 of the proper age. But this is not the case. In the chick 

 tlie development of the Wolffian tubules behind is very 

 different to that in front. This fact has apparently been 

 overlooked by the most recent observers. 



The development of the Wolffian body in the duck is 

 much more completely similar throughout than in the chick, 

 and reference will be at first made to figs. 2 — 5, taken from 

 a duck embryo with thirty-one or thirty-two protovertebrse, 

 in the following description. 



' ' Arch. f. Mic. Anat.,' Bd. 1. 



2 ' Untersuchungen iiber d. Entwick. des Urogen. systems beim 

 Hvihnchen,' Diss. Inaug., Riga, 1867. 



' Loc. cit. 



* The term segment is used as equivalent to protovertebra, muscle 

 plate. 



