398 HARRY H. CHARLTON 



Thompson ('17, p. 267) suggests the formation of the undulat- 

 ing membrane from a free flagellum in the Trypanosomes, as 

 follows: "It is a plausible assumption to suppose that, as the 

 flagellum waves about it conies to lie near and parallel to the 

 body of the cell, and that the frill or undulating membrane is 

 formed by the clear fluid protoplasm of the surface layer spring- 

 ing up in a film to run up and along the flagellum, just as a soap- 

 film would be formed in similar circumstances." Of course the 

 axial filament in this case is located between the nucleus and the 

 outer cell wall, but it seems a reasonable hypothesis to think of 

 the axial filament as having become loose from the nucleus 

 and as able to draw out the thin layer of cytoplasm some little 

 distance from the nucleus forming the undulating membrane. 



The nucleus and middle-piece now become drawn out to 

 considerable length, the acrosome decreases in size and we see a 

 slight projection of the nucleus extending beyond the acrosome. 

 The elongated nucleus stains darker and darker until no structure 

 can be made out. From this point until the mature spermatozoa 

 are reached I have not been able to make observations (figs. 

 93 and 94). 



The spermatozoa 



A study of the mature spermatozoa has been made by teasing 

 the contents of the seminal vesicle in a minute quantity of physi- 

 ological salt solution and either studying them alive in the solu- 

 tion or fixing the teased material in osmic acid fumes, hot corrosive 

 sublimate, Bouin or strong Flemming, and staining. 



The unstained living contents make an interesting study 

 when examined by means of the dark-field microscope. In 

 addition to the spermatozoa with their waves of movement 

 extending from anterior to posterior end of the undulation 

 membrane, there are a large number of small elliptical bodies 

 performing active brownian movement. I thought at first that 

 these bodies were the true spermatozoa and the others giant 

 spermatozoa, but further study convinced me that this was not 

 the case, for no tails could be found upon the small bodies, 

 they stained only by plasma stains, and furthermore no stages 

 in their development could be made out. 



