55o 



SPERMATOGENESIS 



(AiAlK 



the sperm (f, g), while the nucleus becomes its more or less 

 spindle-shaped head and the centrosome takes the form of a 

 small intermediate piece at the junction of head and tail. 

 Thus the sperm or male gamete is a true cell, specially 



Fig. 139.— Spermatogenesis in the Mole-Cricket {Gjyllotalpa). 

 A, primitive sex-cell, just preparatory to division, showing twelve chromosomes 

 (c/fr); c. the centrosome. B, sperm-mother-cell, formed by the division of A, 

 and containing twenty-four chromosomes ; the centrosome has divided into two. 

 C, the sperm-mother-cell has divided into two by a reducing division, each 

 daughter-cell containing twelve chromosomes. D, each daughter-cell has divided 

 a^am in the same manner, a group of four sperm-cells being produced, each 

 with six chromosomes. E^a single sperm-cell about to elongate to form a sperm. 

 F, immature sperm ; the six chromosomes are still visible in the head. G, fully 

 formed sperm. (From Parker's Biology, after vom Rath.) 



modiiied in most cases for active movement. This actively 

 motik', tailed form is, however, by no means essential : in 



