348 



REPRODUCTION 



These changes constitute the maturation of the sperma- 

 tozoa and have their counterpart in similar changes 

 undergone by the ovum. 



Structure of Spermatozoa 



The human spermatozoon consists of three parts, a 

 flattened ovoid head, a small cyhndrical body, and a long 

 tail which consists of a filament embedded in protoplasm. 

 The head constitutes the nucleus and contains chromatin. 



SPER.MAT060NIUM 



SPERMATOCYTE 



HETER.OTYPE.\ 

 Dl VISION I 



SECONDARY 

 SPERMATOCYTES 



SPERMATIDS 



* d d # 3PERJ<ATOZ.O^ 



Fig. 64. — Scheme of spermatogenesis (after Boveri). 



The tail runs through the middle of the body, arising from 

 the base of the head. At the anterior part of the head is 

 an apical projection known as the achrosome. The 

 motiUty of a spermatozoon is due to a lashing movement 

 of its tail. 



Accessory Sexual Glands 



The seminal vesicles consist of convoluted tubes opening 

 into the termination of the vas. They secrete a fluid 

 which nourishes and stimulates the spermatozoa. 



