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 \ 



Germ Cells Proper 



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 



