310 FERNANDUS PAYNE 



the cytoplasm of the tail and is thrown off. The elongated 

 body remains to form the acrosome. It migrates to the side 

 of the nucleus opposite the mitochondrial mass (plate 2, F to K) 

 and condenses into a cone shaped cap (plate 3)._ 



4. THE MIDDLE-PIECE 



In Gryllotalpa the middle-piece arises from the same body 

 from which the axial filament grows (plate 2, G). As the middle- 

 piece has been described as arising from the- centrosome in prac- 

 tically all cases, the presumption is that this body is a centro- 

 some. It is only a presumption, however, as I have not been 

 able to trace the body back to the centrosome of the second 

 spermatocyte division. Whatever this small body may be, it 

 undergoes considerable change in its transformation into the 

 middle-piece. It first divides, or in some manner gives rise to 

 a double structure, the two parts of which are at first approxi- 

 mately equal in size (plate 2, J). This equality changes with 

 the enlargement of the basal granule (plate 2, K and plate 3, 

 A, B, C, D). The double structure next changes to a more or 

 less flattened single body (plate 3, E and F), which again soon 

 changes to a double structure (plate 3, K). This double struc- 

 ture, when viewed from below, appears as two half moons 

 (plate 3, I). At this time the axial filament can no longer be 

 seen. The last stage in which the middle-piece is visible is shown 

 in plate 3, 0. The two parts here are again unequal. In the 

 later stages of the development of the spermatozoon there are 

 no traces of the middle-piece. 



5. DISCUSSION OF ACROSOME AND MIDDLE-PIECE 



In a study of the transformation of the spermatid into the 

 spermatozoon I have been impressed with the small amount of 

 cytoplasm which goes into the spermatozoon. Masses of it seem 

 to be thrown off along the tail (plate 3, J). In the mature 

 spermatozoon, certainly, there can be no more than a thin film 

 surrounding the nucleus and tail. In fact, no cytoplasm can be 

 seen around the nucleus. However, the acrosome, middle-piece 

 and tail are extranuclear structures, and hence of cytoplasmic 



