213 



the organism. In the larval Amphibian, on the other hand, the fun- 

 nels (pronephric) are active and there is great probability for suppo- 

 sing that they form the normal points of exit for the egestive cells. 

 Theoretically we would expect that, if the necessity for the exit of 

 egestive cells from the organism be removed (by reduction of mono- 

 cytic ingestion) then the loss of protoplasm to the organism involved 

 by this exit would be avoided by some adaptation culmiuating in the 

 complete atrophy of the funnels, and the retention of the ek-phoro- 

 cytes in the system. 



Searching for a repetition of phylogenetic history in the ontogeny 

 of the frog, we find in this connection that first the funnels open 



Fig. 9. Fig. 10. 



Fig. 8. 



Fig. 8. Further complication of excretory elements, with formation of glome- 

 rulus igl). Monocytic egestion. (Vertebrate kidney.) 



Fig. 9. Secondary connexion of nephrostome with renal vein , monocytic in- 

 gestion vestigial, except in fat-absorption (?]. Cells returned to vascular system. (On- 

 togeny of Rmm.) 



Fig. 10. Further complication of tubules of Vertebrate kidney, completely 

 and solely excretory in function, and nephrostome closed. (Vertebrate kidney.) 



freely (Fig. 8) into the body cavity (pronephric and mesonephric) 

 and that later the mesonephric funnels obtain a secondary 

 connection by opening into the venous system 3* (Fig. 9). 



This extraordinary anatomical fact can be perfectly accounted for 

 by the above hypothesis, i. e., that it is an adaption to save the loss to 

 the organism of the egestive cells, which are thus returned to the vas- 

 cular system. 



38 »In tadpoles of 18 to 20 mm length, the nephrostomial tubules break away 

 completely from theW^olffian tubules, and acquire openings at their inner ends into 

 the renal veins, on the ventral surface of the kidney«. A. M. Marshall, Verte- 

 brate Embryology. 



