THE WOLFFIAN DUCT AND WOLFFIAX BODY. 



317 



In their mode of development the Wolffian tubules present 

 certain differences in the anterior and posterior parts of the 

 Wolffian body respectively, and must be described separately. 



In front of about the sixteenth somite, a number of small 

 funnel-like depressions of the peritoneal epithelium appear, 

 towards the end of the second day (Fig. 129, KS), below and a 

 little to the inner side of the Wolffian duct. The bottoms of these 

 funnels are in connection with slightly twisted cellular cords, 

 which form in the mesoblast. These cords soon become tubular, 



FIG. 129. A transverse section across the body of a Chick Embryo at the 

 forty-eighth hour of incubation, x 150. 



A, aorta. AN", amiiion. C, body cavity or coeloin. CH, notochord. CM, myocoel, 

 or cavity of mcsoblastic somite. TT, hypoblast forming roof of mid-gut. KG, Wolffian 

 duct. 3Z.S, nepbrostome. ME, somatopleuric layer of mesoblast. MH, Splanchno- 

 pleuric layer of mesoblast. MP, muscle plate. N"E, rudiment of spinal ganglion. 

 NS, spinal cord. OE, genital epithelium. VC, posterior cardinal vein. W, vitelline 

 vein. 



and acquire communications at one end with the funnel-like 

 depressions, and at the other end with the Wolffian duct ; so that 

 the peritoneal funnels, or nephrostomes, now lead from the coelom 

 through these Wolffian tubules into the Wolffian duct. The 

 nephrostomes, and the Wolffian tubules into which they open, are 

 usually from the first rather more numerous than the somites in 

 which they lie. 



The anterior Wolffian tubules are imperfect from the first, 

 and soon undergo degenerative changes. The mouths of the 

 nephrostomes first dilate greatly. A vascular process, or glo- 



