8 4 



Vertebrate Embryology 



body as well. We have now to consider in what way the 

 ureters and generative ducts of the adult frog are formed. 

 About the time of the metamorphosis the head kidney, 



FIG. 31. TRANSVERSE SECTION THROUGH THE BODY OF A TAD- 

 POLE AT THE TIME OF HATCHING ; THE SECTION PASSING THROUGH 

 THE SECOND PAIR OF THE NEPHROSTOMES, AND THE THIRD PAIR OF 



MYOTOMES. X 50. (After Marshall.) 



A, aorta. C, coeolom or body-cavity. Cff, notochord. CJ, subnoto- 

 chordal rod. G M, glomerulus. K P, segmental or archinephric duct. K S, 

 second nephrostome of left side. ME, somatopleuric layer of mesoblast. M H, 

 splanchnopleuric layer of mesoblast. ML, myotome. N L, lateral line branch 

 of pneumogastric nerve. N S, spinal cord. T, intestinal region of mesenteron. 

 V 'C, posterior cardinal vein. VH, hepatic vein. W, liver diverticulum. 



which has become rudimentary, separates completely 

 from the duct, which now ends blindly a short distance 

 in front of the Wolffian body. 



