18 



EDWARD MCCRADY, JR. 



These later disappear. The tail fiber grows out from two 

 centrioles which are situated near the surface at the pos- 

 terior of the cell (fig. 3, A). The nucleus migrates to a point 

 opposite the centrioles (therefore at the anterior of the cell) 

 and becomes condensed into a flattened egg-shaped mass "n 

 which no details are recognizable. The centrioles, which are 

 connected by a fine fiber, follow the nucleus, and the proximal 

 one becomes attached to it (fig. 3, B). The distal one, which 



hu. 



nu. 



Fig. 3 Spermiogenesis (redrawn from Duesberg, '20). A, early spermatid. 

 The idiozome has already broken and released the two centrioles which are now 

 giving rise to the axial filament. Fat globules are numerous, and are always 

 collected into one group. Chondriosomes are filamentou^. B, chondriosomes have 

 become granular. Caudal tube formed. Excrescence still attached to distal 

 centriole. C, the ring has begun its migration. Excrescence attaches separately 

 to swallow-tail nucleus. D, many chondriosomes have collected around axial 

 filament. E, residual body about half formed. F, residual body has been cast off. 

 Chondriosomes have formed spiral around axial filament. Spermatozoon is now 

 free in semeniferous tubule. G, in epididymis the spermatozoa have paired by 

 fusion in the head region along the heavier arm of the V-shaped nucleus. Middle 

 piece now runs between legs of the V instead of at right angles to it. 



