148 
ADAM SEDGWICK. 
Since 1874 the work of Gotte^ and SpengeP on Am- 
phibia, Kolliker^ on Aves, BrauiA on Lacertilia, and Fiiv- 
bringer on Teleostei, Amphibia, and Aves^ has shewn that 
the excretory system of all these animals is developed on a 
type seen in its simplest form in Elasmobranchs. 
Kolliker 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 epi- 
thelium. 
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 1 know, no ideas as to the morphological 
meaning of the Amniote kidney was held before 1874. 
Conflicting statements were then put forward by different 
observers with regard to the actual embryonic development. 
Remak^ and Kolliker® 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 offshoots, 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. Lbwe^ 
has also recently arrived at the same conclusion from his 
observations on Mammals. 
^ ‘ Entwickelungsgesch. d. Unke.’ 
2 “ Das Urogen. system d. Arnphibien,” ‘ Arb. a. d. Zool. Inst.’ 
Wurzburg, 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. 
‘ Entwickelung der Wirbelthiere.’ 
8 Loc. cit. 
® ‘ Centralblatt fur die Med. Wissenschaften,’ Oct., 1879. 
