STUDY OF SECTIONS OF EMBRYO OF 17 MM. 



309 



panded portion of the cavity shown in our figure corresponds in part to the pelvis 

 of the adult organ. Its irregular shape is due to the fact that it is forming a 

 series of outgrowths, which are to give rise to the collecting tubules. Around 

 the ends of the branches of the renal pelvis is a darker tissue, in which the cells 

 are very much crowded. It is the material out of which the glomeruli and con- 

 voluted tubules of the kidney are to be differentiated. By a secondary process 

 these tubules become united with the branches from the renal pelvis, the branches 

 forming the collecting tubules only of the adult organ (compare page no). The 



Nch 



W.D 



FIG. 210. PIG, 17.0 MM. TRANSVERSE SERIES 51, SECTION 759. 



All] Allantois. Ao, Aorta. A.um, Umbilical artery, card, Branch of cardinal vein. Cce, Coelom. G, Gan- 

 glion. Ki, Kidney. N',N V , Nerves. Nch, Notochord. P.L, Posterior limbs. Reel, Large intestine. Sp.c, 

 Spinal cord. Svm, Sympathetic ganglion. W.b, Wolffian body. W.D, Wolffian duct. X 17 diams. 



origin of the renal anlage may easily be followed in earlier stages. It is found that 

 from the pelvic end of each Wolffian duct there develops a dorsal outgrowth, which 

 is lined by epithelium. This outgrowth elongates in a headward direction. Its 

 end expands; the narrow portion is the ureter, the expanded portion the anlage 

 of the pelvis. The pelvis becomes irregular in shape and forms outgrowths. 

 Around it appears the condensed tissue just referred to. On the ventral and 

 lateral sides of the kidneys in our section appear the ends of the Wolffian bodies, 

 W.b. From the ventral and inner edge of each Wolffian body is a projecting lobe 

 of tissue in which the Wolffian duct, W.D, is lodged. The walls of the Wolffian 

 duct are a rather thin, cuboidal epithelium, surrounded by mesenchyma in which 

 there is no very clear evidence of specialization. Between the Wolffian bodies 





