KIDNEY IN RELATION TO WOLLFJAN BODY IN TBE CHICK. 69 



serial ingrowths of the hody-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 back 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 (kb). 



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 

 protovertebrae. 



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 



