VI.] THE WOLFFIAN BODY. 191 



The tubules of the Wolffian body are developed 

 independently of the Wolffian duct, and are derived 

 from the intermediate cell-mass, shewn in Fig. 34, 

 between the upper end of the body-cavity and the meso- 

 blastic somite. In the chick the mode of development 

 of this mass into the segmental tubules is different in 

 the regions in front of and behind about the sixteenth 

 segment. In front of about the sixteenth segment 

 special parts of the intermediate cell-mass remain 

 attached to the peritoneal epithelium, on this layer 

 becoming differentiated ; there being several such parts 

 to each segment. The parts of the intermediate cell- 

 mass attached to the peritoneal epithelium become 

 converted into S-shaped cords (Fig. 64 st) which soon 

 unite with the Wolffian duct (wd), and constitute the 

 primitive Wolffian tubules. Into the commencement 

 of each of these cords the lumen of the body-cavity is 

 for a short distance prolonged, so that this part con- 

 stitutes a rudimentary peritoneal funnel leading from 

 the body-cavity into the lumen of the Wolffian tubule. 



In the foremost Wolffian tubules, which never reach 

 a very complete development, the peritoneal funnels 

 widen considerably. The section of the tube adjoining 

 the wide peritoneal funnel becomes partially invaginated 

 by the formation of a vascular ingrowth known as a 

 glomerulus, and this glomerulus soon grows to such an 

 extent as to project through the peritoneal funnel, the 

 neck of which it completely fills, into the body-cavity 

 (Fig. 66, gl). There is thus formed a series of glomeruli 

 belonging to the anterior Wolffian tubuli projecting 

 freely into the body-cavity. These glomeruli with 

 their tubuli become however early aborted. 



