GERM CELLS OF ARGAS 663 



layer marked by striations which run perpendicular to the 

 surface. 



The extra-nuclear bodies appear early in the growth period. 

 They are first seen within the nucleus, later pass through the 

 nuclear wall, and finally become widely scattered in the cyto- 

 plasm, where they are dissolved and absorbed before the time of 

 maturation. Their behavior and staining reactions suggest that 

 these bodies are similar in nature to the plasmosome or true 

 nucleolus. 



The vesicular bodies are formed de novo in the cytoplasm at 

 about the time the extra-nuclear bodies appear, but no apparent 

 relationship exists between the two. When first seen they appear 

 as fusiform fibers but as they increase in number the fibers open 

 out to form vesicles (v.b., fig. 5). These bodies are evenly dis- 

 tributed in the cytoplasm until after the formation of the sperma- 

 tids, when they collect near the nucleus at one side of the cell. 

 Here they gradually disintegrate and, as they are breaking down 

 and disappearing (fig. 15), droplets of a fatty nature (o.d.) are 

 deposited in the cytoplasm which surrounds them. The vesicu- 

 lar bodies are considered as mitochondrial in nature for they 

 fulfill several, although not all, of the tests employed in deter- 

 mining mitochondria. 



The true mitochondria are present in the youngest sperma- 

 togonia examined, and they persist, with certain modifications 

 of arrangement and form, throughout the entire history of the 

 developing spermatozoon. In the young spermatids (fig. 13, 

 a.m.) mitochondria begin to collect at the side of the cell oppo- 

 site the nucleus, where many of the granules fuse together and 

 form a massive ring (figs. 15 and 16, m.r.). Later, when the 

 mitochondrial ring breaks up (fig. 23) the granular mitochondria 

 are not widely scattered but are carried in a mass to a particular 

 region of the forming spermatozoon. 



The transformation of the spermatid into the spermatozoon is 

 initiated by (1) the migration of the nucleus to one side of the 

 cell, (2) the formation of the mitochondrial ring (3) the move- 

 ment of the vesicular bodies toward the nucleus and their later 

 disintegration, and (4) by the disappearance of the outer striated 



