No. 4-] MALE REPRODUCTIVE CELLS OF INSECTS. 1 91 



of the nucleus take in the formation of the spermatozoon, but 

 in the light of present knowledge it appears as if the accessory 

 chromosome was prominently concerned in the formation of 

 the head. The nucleolus-like body that results from the last 

 spermatocyte division, which has again taken ^, 

 up its position on the surface of the nucleus, 

 becomes vacuolated and forms a covering for 

 the nuclear vesicle. Gradually this collects at 

 the end of the pear-shaped vesicle, and by the 

 usual process of condensation and arrange- ^ 



^ ^ Fig. 13. — Spermatid 



ment of the chromatic and achromatic parts showing the strongly 

 of the cell the spermatozoon is formed. cil^omos^me'TnTZ 



]^t being the purpose of the present article weakly staining chro- 

 merely to call attention to the changes taking 

 place in the accessory chromosome, no attention will be paid 

 to the part played by the other cell structures, except as they 

 have some bearing upon the behavior of this body. 



In seeking to point out the features that characterize this 

 peculiar nuclear element, perhaps the most striking thing to be 

 noticed is the almost uniform staining power exhibited. While 

 the ordinary chromatin gradually and progressively weakens in 

 staining ability, the accessory chromosome retains its original 

 affinity for the haematoxylin and basic anilines undiminished. 

 As a consequence of this, in all the cells of the testes, the 



accessory chromosome is at once 

 distinguishable. Only in the early 

 spermatogonia, when the chroma- 



FiG. 14. — Almost mature spermatozoon. 



tin Stains most strongly, is there 

 any difficulty in observing this peculiar element. As the cells 

 progress toward the formation of the spermatozoon, a greater 

 and greater difference arises between the chromatin and its 

 companion element, until in the spermatid so preponderant 

 has become the volume of the accessory chromosome that one 

 is almost irresistibly driven to the conclusion that it is chief in 

 importance. 



This variation in staining capacity of the chromatin and 

 nucleolus Q) has not escaped the observation of other investi- 

 gators. In describing: the staining; reaction of the different 



