GERM CELLS IN THE ARTHROPODA 131 



generation. This rod is considered by Montgomery 

 to be of cytoplasmic origin and is termed by him a 

 " Sertoli cell determinant." During the division 



Antepenultimate 

 Spermatogonium 



Penultimate 

 Spermatogonia 



Ultimate 

 Spermatogonia 



Sertoli y ^^__^ -, 

 cell \^ i ^^■' 



Fig. 42. 



Diagram illustrating the differentiation of the Sertoli cell in 

 man. (From Montgomery, 1911.) 



of the antepenultimate spermatogonia the rod passes 

 undivided into one of the daughter cells ; thus one- 

 half of the penultimate spermatogonia possess a 



