THE MORPHOLOGY OF FERTILIZATION 



49 



concentrated chromatin of the nucleus, including always, 

 as its history shows, the haploid number of chromosomes. 

 It frequently bears anteriorly a process called for obvious 



-s 



A 



C 



D 



Fig. I. — Spermatozoa of various animals: A, Diagram of the 

 flagellate spermatozoon (after E. B. Wilson): i, perforatorium; 2, 

 acrosome; 3, nucleus; 4, centrosome (end knob); 5, middle piece; 6, 

 involucre (envelope) of the tail; 7, axial filament; 8, end piece. B, 

 Spermatozoon of a crab (Maia, after Grobben). C, Spermatozoon of 

 a bird {Phyllopneuste, after Ballowitz). D, Spermatozoon of a sala- 

 mander {Amphiuma, after McGregor). 



reasons the perforatorium. There is usually no distin- 

 guishable cytoplasmic mantle around the nucleus, 

 though theoretically such a mantle should be present. 

 The. middle piece usually includes the centrosomal 



