104 CYTOPLASMIC STRUCTURES [CH. 



which have been shown by MONTGOMERY (1911 b] to be de- 

 rived by a differential division from the primitive spermato- 

 gonia (cf . PL X). The manner of their differentiation will be 

 described in Chapter XII; their function appears to be 

 to act as nutrient cells for the developing spermatozoa, 

 bundles of which become attached to them. In some insects 





FIG. 15. Verson's cell in testis of a butterfly (Pieris brassicae) surrounded 

 by developing spermatocytes. 



a. Synizesis ; b. emergence of chromosomes from synizesis. 

 c. Growing spermatocytes becoming arranged in cysts. (Writer's 

 preparation.) 



each compartment of the testis contains a large Person's 

 cell, around which the spermatogonia are aggregated, and 

 which in the same way appears to serve as a channel for the 

 supply of nutriment to the sperm-cells. In a number of 

 invertebrates the spermatozoa develop in connection with 

 a protoplasmic mass known as a cytophore, from which the 

 spermatogonia are produced by repeated nuclear division, 



