70 KANSAS UNIVERSITY QUARTERLY. 



seen until the stage represented in fig. 30 is reached, when it has 

 taken up its jjosition near the nucleus, at one side of the opening in 

 the nuclear membrane. At the time of the disappearance of the cen- 

 trosorae, masses of deutoplasm have become abundant in the cell, and 

 it is very probable that this element is merely concealed by one of 

 these and that it will be found on further study. 



As before stated, the pathway left by the itomere in its passage 

 through the cytoplasm can be easily distinguished. As the cell in- 

 creases in size, this, instead of becoming more faint, as one might ex- 

 pect, gradually becomes plainer and more easily distinguishable (figs. 

 29-33), until, in the stage represented in fig. 34, it stands out as a 

 densely staining black line — the axial filament. This is formed, not 

 by an outgrowth or elongation of the centrosome, as has been de- 

 scribed for other objects, but by the collection and condensation of 

 the fibers of the cytoplasmic reticulum. In earlier stages (fig. 32), a 

 cross-section of the pathway left by the itomere shows a rather 

 diffusely staining area, toward which the fibers composing the reticu- 

 lum converge as toward a centrosome. At this stage, however, the 

 centrosome can be clearly distinguished at a point near the nucleus 

 and at one side of the position subsequently occuj)ied by the axial 

 filament. Later, it moves directly into the course of the future axial 

 filament, which, at this period, stains more densely, and, although 

 still somewhat granular and indefinite in appearance, stands out much 

 more distinctly than at any jjrevious time. (Figs. 33, 34.) 



While this is taking place the cytoplasm becomes vacuolated in 

 the region surrounding the axial filament. The large, rather elongated 

 vacuoles extend with their longer diameters approximately parallel to 

 the course of this structure. 



The significance of this vacuolation appears to be in the fact that 

 the previously fine reticulum is being broken down and reformed into 

 fibers extending parallel to the axial filament, thus leaving large 

 clear spaces in the cytoplasm. In later stages these fibers become col- 

 lected and condensed, and in the mature spermatozoon, although they 

 still preserve their individuality, cannot be distinguished from each 

 other without the aid of maceration. The origin of the axial fila- 

 ment in Scolo})endra from the fibrillar reticulum of the cytoplasm 

 agrees with the discoveries by Ballowitz^ of the fibrillar character of 

 this element in spermatozoa. He describes it as being made up of a 

 large number of parallel fibrillar. 



The axial filament being thus definitely formed, farther changes 

 consist in its elongation, and this continues until it is several hundred 

 micra in length. Its later growth is accompanied by a corresponding 



6. Ballowitz, E., 1891: " Weitere Beobacbtungen uber den feinerea Bau der Saugethier- 

 spermatozoen." Zeitscbrift fur wissenscbaftlicbe Zoologie. Bd. LII. 



