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 



^fj5^ *? v': ; -- -: '& '. vj ' 



''"'''Mfe^^-^ 



FIG. 15. Verson's cell in testis of a butterfly (Pieris brasslcae] 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 Ver sorts 

 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, 



