KIDNEY IN RELATION TO WOLLFIAN BODY IN THE CHICK. 153 
serial ingrowths of the body-cavity epithelium, for this thin- 
ning of the peritoneal epithelium, adjoining the region where 
they will appear, is continuous, i. e. cells must grow in along 
a line extending the whole length of that part of the body- 
cavity which the Wolffian body adjoins. 
The development of the Wolffian blastema, so described, is 
continued as far hack as the » opening of the Wolffian duct 
into the cloaca, which occurs in the thirty-fourth segment. 
In fig. 12 it may be seen in the thirty-second segment (kh). 
The Wolffian blastema of the chick then develops in two 
slightly different ways. 
In the anterior part, about as far back as the twentieth 
(fig. 1) segment, that process of development which has been 
described at length in the case of the duck (in which animal 
it is apparently the only method of development) is passed 
through in the chick. 
Posteriorly from the twentieth segment the intermediate 
cell mass has never any connection with the peritoneal epi- 
thelium, and gives rise to the Wolffian blastema quite inde- 
pendently of the peritoneal epithelium. This latter process 
is clearly an abbreviation of that which takes place through- 
out in the duck and in the anterior part of the chick. 
I have mentioned the twentieth segment as about the limit 
between the two. I cannot fix the exact limit. 
It has been stated above that in the case of the duck and 
the anterior part of the chick (figs. 1, 2, 4) the intermediate 
cell mass becomes, at certain points, very markedly con- 
tinuous with the peritoneal epithelium, and appears to en- 
close a prolongation of the body-cavity (fig. 1 and fig. 2). 
Such connections are undoubtedly rudiments of the nephro- 
stomata seen in other Vertebrates. They do not occur seg- 
mentally, being situated as often as not between the 
protovertebrse. 
Rudiments of these rudimentary nephrostomata occur in 
the posterior part of the chick’s Wolffian body ; that is, 
although a fairly sharp line can always be drawn between 
the Wolffian blastema and the peritoneal epithelium, yet 
the cells of the latter, at certain points, arrange themselves 
just as they do in front, where the line of the body-cavity is 
continued into the intermediate cell mass. These latter 
rudiments are very obscure, and I have been unable to make 
any satisfactory determination of their number. They may 
be due merely to an accidental arrangement of the cells, 
which might occur in consequence of the bend in the peri- 
toneal epithelium at this point. Whether the rudimentary 
nephrostomata in the anterior part of the chick’s kidney 
