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 

 Spermatogonlum 



Penultimate 

 Spermatogonia 



Ultimate 

 Spermatogonia 



000 



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 



