344 ELEMENTARY PHYSIOLOGY. [XXXII. 



4. Tease out in dilute glycerine a fragment of a 

 testis which has been placed in osmic acid *5 p.c. 

 for a day and observe the cells and developing 

 spermatozoa of the tubuli seminiferi. 



5. Cut in half the fresh testis of a rat, and gently 

 press the cut surface on a glass slide. Observe 

 the spermatozoa, each consisting of 



a. An ovoid head or body. 



6. A long tapering tail or process. 



c. A short intermediate part. 



Note that the spermatozoa move by a whip-like 

 movement of their tails. 



6. Observe in like manner the spermatozoa of a 

 newt. The head is long and pointed, the inter- 

 mediate part small and not very distinct ; from 

 the intermediate part starts a filament which 

 runs in a spiral around the long tail; the filament 

 is in reality the edge of a thin spiral membrane, 

 but this is difficult to make out. 





