64 ADAM SEDGWICK. 



of other observers, before 1874, were identical with one or 

 the other of these. 



Since 1874 the work of Gotte^ and SpengeP on Am- 

 phibia, KoUiker^ on Aves, Braun* on Lacertilia, and Fiir- 

 bringer on Teleostei, Amphibia, and Aves^ has shown that 

 the excretory system of all these animals is developed on a 

 type seen in its simplest form in Elasmobranchs. 



KoUiker first discovered in Aves structures composed of 

 strings of cells connected with the Wolffian duct and peri- 

 toneal epithelium, and placed just ventral and internal to the 

 former. These he compared to the early segmental tubes 

 described in Elasmobranchs. From the similarity of these 

 structures to those seen in Elasmobranchs and from his 

 own observations he was led to assert for them a deve- 

 lopment similar to that described for Elasmobranchs, viz. 

 from segmental involutions of the body-cavity epithelium. 



In this he was followed by Fiirbringer,^ except in a small 

 detail, the latter observer denying that these cell strings had 

 any lumen opening into the body-cavity. 



So far as I know, no ideas as to the morphological 

 meaning of the Amniote kidney were held before 1874. 



Conflicting statements were then put forward by different 

 observers with regard to the actual embryonic development. 

 Remak''' and KoUiker^ maintained that the whole of the 

 epithelium of the kidney tubules, including that of the 

 collecting and secreting tubules and the Malpighian bodies, 

 was derived from a simple outgrowth from the ureter. 



The condensed mesoblast tissue which lies near the ureter 

 and its oflshoots, in their opinion, only gives rise to the 

 connective and vascular elements of the kidney. 



Kolliker has expressed this view in the second edition of 

 his great work on the development of Vertebrates. Lovve^ 

 has also recently arrived at the same conclusion from his 

 observations on Mammals. 



^ ' Entwickelungsgesch. d. Unke.' 



* "Das Urogen. system d. Amphibien," *Arb. a. d. Zool, Inst.* 

 AVurzburg, Bd. 3, 1876. 



' * Ent. gesch. d. Menschen u. d. hoheren Thiere.' 



* " Das Urogen-system d. d. Einheimischen Reptilien,' Semper's ' Ar- 

 beiten,' Bd. 4. 



* " Zur vergleichenden Anat. u. Entwickelungsgeschichte d, Excre- 

 tionsorgane der Vertebraten," ' Morphol. Jahrbuch,' Bd. 4. The reader 

 is referred to this admirable essay for the literature, and a complete ac- 

 count of our knowledge of the excretory organs of Vertebrates. 



" Loc. cit. 



7 'Entwickelung der Wirbelthiere.' 



^ Loc. cit. 



» • Centralblatt fiir die Med. Wissenschaften/ Oct., 1879. 



