128 



GENERAL EMBRYOLOGY 



COMPARISON OF THE STRUCTURES OF THE SPERMATID AND 

 SPERMATOZOON 



With particular reference to the mammalian condition. (Partly from 



Gegenbaur-Fiirbringer, Lehrbuch der Anatomie des Menschen, 



Leipzig, 1909) 



SPERMATID 

 Nucleus. 



Spermatosphere (centre- 

 sphere) . 



Proximal centrosome (cen- 

 triole) . 



Distal centrosome (cen- 

 triole) . 



(a) Anterior portion. 



(b) Posterior portion. 



Cell body. 



SPERMATOZOON 



Head. 



Mitochondria. 



Acrosome (perforat-orium) and sheath 

 covering the anterior part of the head. 



Forms an undifferentiated part of the 

 middle piece; in Mammals, the neck. 

 In part may disappear. 



Centrosome of middle piece. 

 Annulus and axial filament of middle 

 piece and tail. 



Partly used as source of energy during 

 metamorphosis. Partly thrown off. 

 Remainder forms cytoplasmic envel- 

 opes of middle piece and tail (includ- 

 ing undulatory membrane) . 



Spiral membrane of middle piece. 



Whatever the details of the metamorphosis of the spermatid 

 may be, the facts of essential importance are always identical. 

 These are, that the nucleus of the spermatid is directly trans- 

 formed into the head of the spermatozoon; the centrosomes 

 of the spermatid become the centrosomes and kinoplasmic 

 structures of the spermatozoon and are contained within the 

 middle piece, or partly in the tail; the cytoplasm of the sper- 

 matid in part goes to form a thin cytoplasmic investment of the 

 spermatozoon or is in part cast off. 



The fully formed spermatozoa now lose connection with the 



