Tonephric funnels 



glomerulus 



dorsal aorta 



nephric duct 



second 

 pronephric tubule 



dorsal aorta 



Figure 10-29. Development of the kidney of the lamprey. A, cross section of 15-mm larva; 

 B, ventral view of pronephric tubules as they lie in the pronephric sinus; C, stereodicgrom of the 

 anterior pronephric tubule of a 15-mm larvo; D, cross section in the mesonephric region of a 15-mm 

 larva, about middle of body; E, parasagittal section of a well-developed mesonephros. (E after 

 Gerard, 1954) 



THE EXCRETORY SYSTEM • 315 



