THE LATER DEVELOPMENT OF THE FROG 199 



;onnections of the inner tubules with the pronephric duct 

 convert this into the mesonephric or Wolffian duct, which 



>mains as the ureter of the mesonephros or definitive kidney. 



"he inner tubules elongate and become coiled, forming the 

 tubular portion of the later kidney. 



Mt 



my 



m 



pc 



80 



w 





FIG. 73. Sections through the developing mesonephros and the commoa 

 jphrostome of R. sylvatica. After Hall. A. Section through the eighth somite 

 an 8.5 mm. larva. B. Section through the mesonephric rudiment of a 25 mm. 

 C. Section through the common nephrostome of a 25 mm. larva, o, 

 jrsal aorta; c, co3lom; en, common nephrostome; g, germ cell; i, inner tubule; 

 mesonephric rudiment; my, myotome; o, outer tubule; p, remains of prone- 

 )hros; pc, posterior cardinal vein; s, shelf cutting off the common nephrostome 

 from the remainder of the ccelom; so, somatic mesoderm; sp, splanchnic meso- 

 srm; W. Wolffian duct; /, primary mesonephric tubule; II, secondary meso- 

 iphric tubule. 



Subsequently the outer tubules have a rather unusual history 

 the frog. From the proximal portion an outgrowth appears, 

 rtiich forms the capsule (Bowman's capsule) around the glo- 



