146 
ADAM SEDGWICK. 
Development of the Kidney in its relation to Wolffian 
Body in the Chick. By Adam Sedgwick, B.A., Scholar 
of Trinity College, Cambridge ; Demonstrator in the 
Morphological Laboratory. (With Plates XVII, 
XVIII.) 
This paper contains an account of observations on the 
development of the excretory system of the chick, made with 
a view of elucidating the relation 'which the kidney bears to 
the Wolffian body. 
The Wolffian body in the embryo chick attains to a very 
great development, but almost completely atrophies in the 
adult, a small part only persisting in the male as part of the 
testicular apparatus. 
In the embryos of lower Vertebrates, viz. most of the 
Icthyopsida, there is present, similarly, an organ called the 
Wolffian body, which, however, much more completely 
persists in the adult, functioning in part as kidney and in 
part as semen carrier. 
The separation into an urinary part and into a sexual part 
is much more complete in some forms than in others. In 
the Elasmobranchii, for instance, the posterior part of the 
embryonic Wolffian body gives rise in the adult to a well- 
developed gland, the kidney, while the anterior part attains 
a far less development ; in fact, more or less retrogrades in 
the adult ; but in the male a part of it enters into connection 
with the testis. 
In the Amniota the case is different. In them an embryonic 
organ, called the Wolffian body, does not function at all in 
the adult as an excretory organ ; it almost completely atro- 
phies from its embryonic perfection, only a small part per- 
sisting in the adult male as the epidydimis. The organ 
which functions as kidney in the adult arises at a relatively 
late stage, and is not apparently, as in Elasmobranchs, a 
modified part of the hind end of the embryonic Wolffian 
body. What, then, is the kidney of the Amniota ? Is it an 
organ which has arisen de novo in the Amniota, or can it, by 
a more accurate study of its development, be traced into 
relation with the embryonic excretory system ? In other 
words, can any evidence be obtained by the study of develop- 
ment proving that the kidney of the chick phylogenetically 
has been modified from part of the same primitive organ as 
that from which the Wolffian body developed, as is the case 
in the Icthyopsida ? 
