GERM CELLS OF ARGAS 659 



The mitochondria are densely collected at the outer or distal 

 end of the inner tube and when the tube is fully formed all of 

 these granules lie in its distal third. Between the stage shown 

 in figure 27 and that of figure 28 the cilia-like processes upon the 

 tip of the inner tube vanish, and in their place is a clear hemi- 

 spherical vesicle which may possibly represent the substance 

 formerly seen in these processes. 



During the growth of the inner tube the nucleus migrates 

 extensively. As shown in figure 28 it still lies at the bases of 

 the two tubes, but shortly afterwards it moves around to the 

 outer surface of the outer tube and begins to travel along this 

 tube toward the opposite end. The outer tube is at this time 

 covered with a gelatinous sheath through which the nucleus 

 moves. By the time the inner tube has reached its full exten- 

 sion the nucleus lies opposite its distal end, and upon the outer 

 surface of the outer tube (fig. 30). While these rearrangements 

 are occurring, the finger-like process progressively shortens (figs. 

 29-30), and some of the substance of which it was composed is 

 apparently absorbed into the basal ends of the two tubes. 



In the condition shown in figure 30 the spermatozoa leave the 

 male tick and their development is completed within the genital 

 ducts of the female, where they are at first packed together in 

 sac-like spermatophores, and later lie freely in, the oviduct. 

 Figure 31 represents a spermatozoon from a spermatophore sac. 

 By comparison with figure 30 it will be noted that the older 

 spermatozoon is now in the form of a single tube with the mito- 

 chondria at one end and the nucleus at the other, and that its 

 total length is about twice that of the spermatozoon shown in 

 figure 30. See also text-figure 1. In -accomplishing this meta- 

 morphosis the mitochondria-filled end of the inner tube pushes 

 through the distal end of the outer tube (at a, fig. 30) and con- 

 tinues its advance, while the outer tube slips backward along the 

 outer surface of the inner tube until at last outer and inner tubes 

 are merged into one continuous structure. As a result of this 

 process the outer tube is turned completely inside out, and the 

 end which was formerly around the mitochondria-bearing end 

 of the inner tube now lies at the opposite end of the spermatozoon 



