MALE ORGANS OF REPRODUCTION 



485 



Acroaome 



Head 4 



Neck 



Body . 



End ring - 



Galea capitis 



Anterior knob 



- Spiral fibers 



... Sheath of axial 

 thread 



cells involved in spermatogenesis. As concerns details, the criteria 

 above given for the grasshopper testis, can be applied. 



The Spermatozoon. Spermiohistogenesis, however, differs some- 

 what. The spermatid nucleus becomes progressively more compact, 

 chromatic and smaller. At the same 

 time it moves toward one pole of the 

 cell, the cytoplasm flowing back- 

 ward, except for a thin envelope 

 (galea capitis) which terminally 

 forms a covering for the perfora- 

 torium which represents a portion 

 (acrosome) of the original idiozome. 

 The idiozome is the germ-cell repre- 

 sentative of the archoplasmic com- 

 plex. Concurrently with the changes 

 outlined for the nucleus it liberates 

 a centrosome, and centrosome and 

 acrosome pass to opposite poles of 

 the nucleus. The centrosome di- 

 vides into two moieties, a proximal, 

 which becomes attached to the nu- 

 clear membrane, and a distal, which 

 moves peripherally at the same time 

 sprouting a flagellum, the central 

 filament. Meanwhile a peripheral 

 portion separates from the more 

 central portion of the distal centro- 

 some and moves backward over the 

 central filament enclosing an envel- 

 oping column of cytoplasm, the mid- 

 dle piece, in which mitochondria 

 have aggregated. The mitochondria 

 fuse to form a filament, the spinil 

 filament, which becomes spirally ar- 

 ranged about the central filament, 

 grow distally beyond the final locus of the ring centrosome, and together 

 with an envelope of cytoplasm constitutes the tail of the spermatozoon. 

 A short terminal naked portion of the central filament is known as the 

 terminal filament. 



Summarizing the above: The nucleus becomes the head of the 



Main segment of 

 tail 



Axial thread 



Capsule 



Terminal filament 



FIG. 430. DIAGRAM OF HUMAN SPER- 

 MATOZOON. 



(After Bonnet.) 







The central filament continues to 



