GERM CELLS OF ARGAS 665 



of this tube and at the opposite end of the continuous sperm- 

 tube. A flagellum-like process (/), which is probably derived 

 from the finger-form process, lies within the nuclear end of the 

 tube. 

 . Metamorphosis is completed by the protrusion of the flagellum 

 from the nuclear end of the spermatozoon (fig. 33) and by the 

 formation of a circlet of mobile processes at the opposite or 

 mitochondria-bearing end of the sperm. In locomotion the end 

 of the spermatozoon which bears the mitochondria goes first 

 and it would appear that the contractile elements which make 

 locomotion possible are of mitochondrial origin. 



The end of the spermatozoon which bears the nucleus is inter- 

 preted as the morphological head, and the flagellum (which is 

 not mobile) probably represents the acrosome of more typical 

 spermatozoa. 



