272 EMBEYOLOGY OF THE LOWER VERTEBRATES ch. 



Rana temporaries— Bouin) the total number of gonocytes in the 

 gonad undergoes a remarkable reduction, e.g. from between 200 and 



sr-s. 



Fig. 141. — Development of the gonad in Amphibia as seen in transverse sections. 

 (A, after Schapitz, 1912 ; B-E, after Bourn, 1901.) 



A, larva of Axolotl (AwMystoma, mexicana) ; B, Rana temporaria, 20 mm. tadpole ; C, 24 mm. tadpole ; 

 D, 33 mm. tadpole ; E, 35 mm. tadpole with hind legs completely developed. Jol, nucleus of follicle- 

 cell ; £./, .genital fold ; g.s, genital strand; gc, gonocyte ; t/ci, transitional stages showing conversion 

 of apparently indifferent cells into gonocytes ; mes, mesenchyme ; som, somatic mesoderm ; spl, 

 splanchnic mesoderm ; y, yolk. 



250 in a frog tadpole of 26 mm. to between 37 and 46 in a tadpole 

 of 33 mm. (Bouin). During this process individual gonocytes 



