WOLFFIAN DUCT AND BODY IN THE CHICK, 437 
that the continuous ridge extends from the 7th to the 11th 
segments. 
With regard to Gasser’s statement of the complete isolation 
of the duct in the anterior region from the intermediate cell 
mass, I can only say that my observations point to an entirely 
different conclusion. 
Thirdly, I differ with him in his statement that the duct in 
the growth back from the attached extremity does not come 
into relation with adjacent structures. 
As stated above, it seems to me that for the space of four 
segments the small cord of cells which grows back from the hind 
end of the ridge, does almost immediately become connected 
with the intermediate cell mass. 
Development of the Wolffian Duct and Body from the 12¢h—15th 
Segment. 
I now pass to the most interesting point which has turned 
up in my investigations on the excretory system of the chick. 
In a paper by Mr. Balfour and myself in the ‘ Quart. Journ. of 
Micr. Science,’ vol. xix, describing the development of what we 
believed to be a rudimentary head-kidney in the chick, we drew 
attention to a structure which so closely resembled the glomeru- 
lus! of the head-kidney of the Ichthyopsida that we identified it 
as an homologous structure. 
Gasser has also independently discovered and similarly iden- 
tified this structure. 
In the paper just referred to no attempt was made to trace the 
development of this glomerulus, but it was merely described as 
it appeared at the time of its greatest development. 
The following description is taken from that paper : 
“Tn the chick the glomerulus is paired, and consists of a 
vascular outgrowth or ridge projecting into the body cavity on 
each side at the root of the mesentery. It extends from the 
anterior end of the Wolffian body to the point where the fore- 
most opening of the head-kidney commences. We have found 
it at a period slightly earlier than that of the first development 
of the head-kidney....In the interior of this body is seen a 
stroma with numerous vascular channels and blood-corpuscles, 
and a vascular connection is apparently becoming established, if 
it is not so already, between the glomerulus and the aorta. The 
stalk connecting the glomerulus with the attachment of the 
1 T have already given a preliminary account of the development of this 
structure in the ‘ Proc. Cambridge Phil. Soc.,’ May 3, 1880. 
2 *Sitzungsberichte der Gesellschaft zur Bedford d. gesam. Naturwiss.,’ 
No. 5, 1879. 
