BAUMGARTNER : SPERMATID TRANSFORMATIONS. 61 



which is shut off from the cytoplasm by a darkly staining 

 membrane which in sections appears as a ring. This stage 

 persists for some time ; then the nebenkern moves against the 

 axial filament, elongates, loses the ring, and the dark mass 

 passes down along the axial filament. Often it appears in 

 several small drops. 



3. The axial filament does not come from the nebenkern nor 

 from the acrosome. It comes apparently from the nucleus ; 

 probably from the centrosome closely attached to the nucleus. 

 It never passes through the nebenkern — only over its surface. 



4. The acrosome occupies a position in the angle between the 

 nebenkern and the nucleus. It shows a central clear space sur- 

 rounded by a darker mass which stains more intensely on one 

 side. Later it passes to the front of the nucleus and forms the 

 point of the spermatozoon head. 



5. The mature spermatozoon consists of a sharp point, a 

 slender, tube-like head filled with a clear fluid, and a long, 

 thread-like tail. 



Laboratory of Zoology and Histology, 

 University of Kansas. 

 September 27, 1901. 



