WOLFFIAN DUCT AND BODY IN THE CHICK. 21 



intermediate cell mass with the commencing lumen from the body 

 cavitj. 



In the next section the intermediate cell mass is not 

 connected to the peritoneal epithelium. 



In chicks of gradually increasing number of protovertebrae this 

 cavity in the intermediate cell mass gradually becomes more 

 marked (figs. 13, 14), and extends into that part of it imme- 

 diately behind the peritoneal connection (fig. 15). 



Figs, 13, 14, and 15 are three successive sections through the 

 13th segment of a chick with about thirty segments, showing 

 the features of a tubule at this stage. 



The Wolffian duct is connected with the lower end of the in- 

 termediate cell mass in all the three sections. A distinct lumen 

 has appeared in the intermediate cell mass which opens into the 

 body cavity in front (figs. 13 and 14), but is separate from the 

 body cavity in the hindermost section (fig. 15). 



Comparing these figures with figs. 9 and 10 it is seen that 

 fig. 13 or 14 corresponds to fig. 9 in the fact of the continuity 

 between the intermediate cell mass and peritoneal epithelium; 

 while fig. 15 corresponds to fig. 10, in both the continuity 

 having been lost. The difference between them consists in the 

 presence of a distinct lumen in the older series, opening into 

 the body cavity, and continued behind into the part of the 

 intermediate cell mass which has separated from the peritoneal 

 epithelium. This part, marked i. c. m. in fig. 15, will in the 

 next stage become converted into that part of the tubule in 

 which a Malpighian body is developed, while the anterior part, 

 which is open to the body cavity, will widen out considerably, 

 and give rise to a wide peritoneal funnel. 



In fig. 11 is represented a section through a developing 

 Wolffian tubule in the hinder part of the Wolffian body. The 

 tubule {w. t^.) in this section precisely resembles the part of the 

 tubule {i. c. m.) represented in fig. 15. Supposing the anterior 

 part of w. t^. were open to the body cavity it would almost be a 

 repetition of the anterior tubule, save in the fact that it is not yet 

 united to the Wolffian duct. But the hinder tubule (fig. 11) 

 does not develop until after the intermediate cell mass has sepa- 

 rated from the peritoneal epithelium, i. e. subsequent to the 

 obliteration of the rudiment of the peritoneal funnel. 



Not only do the Wolffian tubules in the region of the 12th 

 to 15th segments develop a lumen while still continuous with the 

 peritoneal epithelium, but further, a glomerulus appears in them 

 while still open to the body cavity ; and this glomerulus not 

 only appears in the hinder part of the tubule (fig. 15) which 

 has separated from the peritoneal epithelium, but also in the 

 anterior part (figs. 13 and 14) where it is open to the body 



