4.32 ADAM SEDGWICK. 
On the Harty Devevopment of the AntERIorn Part of the 
Wotrrtan Duct and Bopvy im the CuxicK, together with 
some RemarKs on the Excretory System of the VERTE- 
BraTa. By Avam Sepewicx, M.A., Fellow of Trinity 
College, Cambridge. With Plate XXVI. 
Tue following paper is divided into two parts. The first part 
contains an account of observations on the development of the 
Wolffian duct and anterior Wolffian tubules in the chick, being 
supplementary to my paper on the “ Kidney of the Chick.’”! 
The second part is devoted to a discussion of the vertebrate 
excretory system in general. 
I. Early Development of the Wolffian Duct and Anterior 
Wolffian Tubules in the Chick. 
The first trace of the Wolffian duct is visible in an embryo 
with eight protovertebre as a slight projection from the inter- 
mediate cell mass towards the epiblast in the region of the 7th 
and 8th protovertebre. The projection also extends back 
behind the region of the protovertebre for a short distance. 
In a chick with nine or ten protovertebre a similar condition 
is found, z.e. a projection from the intermediate cell mass 
towards the epiblast in the region of the 7th, 8th, 9th, and 10th 
protovertebre, and for a short distance behind the region of 
the protovertebree. 
In a chick with ten protovertebre the projection is beginning 
to show signs of separation from the intermediate cell mass at 
certain points. The appearance presented by the rudiment of 
the Wolffian duct m the 10th segment of a chick with ten seg- 
ments is shown in fig. 1. 
In a chick with eleven protovertebre the rudiment of the 
Wolffian duct is still present as a projection from the inter- 
mediate cell mass in the region of the 7th, 8th, 9th, 10th, and 
11th protovertebre ; but behind the region of the protovertebrz 
it has grown back for a short distance between the epiblast and 
mesoblast as an irregular cord of cells not connected to the 
peritoneal epithelium. A partial separation of the Wolffian 
duct from the intermediate cell mass is now effected in the 
region of the 7th to the 10th protovertebre. This separation 
is not, however, complete; but the Wolffian duct remains connected 
' «Development of the Kidney in its relation to the Wolffian Body in 
the Chick,” ‘ Quart. Journ. Mic. Sci.,’ vol. xx. 
