648 D. B. CASTEEL 



tion, the extra-nuclear bodies have disappeared and the vesicular 

 bodies are distinctly vesicular or cylindrical in form. 



The details of the process of maturation will not be discussed 

 in this paper since the behavior of the chromatic elements does 

 not bear upon the history of the cytoplasmic inclusions. Imme- 

 diately before the first maturation division the true nucleolus 

 fragments and its elements disappear. The general arrangement 

 of mitochondria and vesicular bodies during this cleavage is 

 shown in figure 10, and figure 11 represents a spermatid imme- 

 diately after the completion of maturation. In both maturation 

 divisions mitochondria and vesicular bodies are apparently evenly 

 distributed to the daughter cells. 



Very shortly after maturation the spermatid exhibits distinct 

 polarity. The nucleus migrates toward the surface of the cell 

 and certain rearrangements occur among the cytoplasmic ele- 

 ments (fig. 12) . The nucleus approaches a point on the surface 

 which is about 30 degrees from the position of the zwischen- 

 korper of the last cleavage. As the nucleus nears the striated 

 layer the striae in its immediate neighborhood disappear. At 

 the same time the mitochondria move in the opposite direction 

 and begin the formation of an aggregate of mitochondrial gran- 

 ules (a.m) at the opposite pole of the cell and somewhat removed 

 from the striated layer. A movement of vesicular bodies toward 

 the nuclear pole, more marked in later stages, begins at this 

 time. Figures 12, 13 and 14 show successive stages in these 

 cytoplasmic rearrangements, leading to the more marked differ- 

 entiations shown in figures 15 and 16. Figure 15 shows the 

 nucleus in contact with the cell wall which is here entirely 

 without striations. The striated layer is now differentiated into 

 two regions, one around the equatorial region of the cell which 

 exhibits no further modification, and a cap-like area at the pole 

 opposite the nucleus where the striations are shorter. The 

 mitochondrial condensation has resulted in the formation of a 

 massive 'mitochondrial ring' (m.r., fig. 16) which lies slightly 

 below the equator of the cell but which in later stages moves 

 toward the nucleus. Nearly all of the mitochondria of the cell 

 are concerned in the formation of this ring and many of the 



