198 C. M. CHILD. 



But these nuclei apparently do not remain massed together in 

 the cytophore. There is every reason to believe that they mi- 

 grate to the periphery. Very frequently cytophores with several 

 old nucleoli imbedded in different regions of their cytoplasm, in- 

 dicating that fragmentation has occurred, show all their nuclei at 

 the periphery as in the case of spermatids formed by mitosis. 

 Since I have never found first spermatocytic mitoses and frag- 

 mentation occurring in the same cytophore and since the nucle- 

 olus disappears before mitosis it seems probable that the presence 

 of the old nucleoli which stain very characteristically and are 

 readily recognizable is sufficient to identify a particular cytophore 

 and its spermatid nuclei, for such, I believe we may call them, at 

 least so far as appearance goes, as the result of fragmentation. 



Fig. 39 (PI. XIV.) is probably a stage in the migration to the 

 periphery of spermatid nuclei formed by fragmentation. At the 

 right of the figure one of the old nucleoli, itself near the peri- 

 phery, and a part of an old nuclear cavity containing a few 

 granules are visible : another lies near the middle of the cyto- 

 phore and still others were found in the same cytophore in 

 other sections. Some of the nuclei have already reached the 

 periphery of the cytophore and the cytoplasm about them bulges 

 from its surface. Most of these nuclei are more or less hemi- 

 spherical with convex surface toward the periphery and a space 

 adjoins the flattened side : this condition is probably connected 

 with the migration of the nuclei toward the periphery. Indeed, it 

 is not impossible that this migration may not be a bodily movement 

 through the cytoplasm of the cytophore, but rather the continued 

 formation of new nuclear membrane on the peripheral side and 

 its continued disappearance on the proximal side. In any case 

 the change of position is probably a " tactic " reaction of some 

 sort. 



In two testes cytophores have been found containing nuclei 

 intermediate in size between those of the spermatocytes at the 

 time of fragmentation and those of spermatids, but which ap- 

 peared as if preparing for fragmentation. Fig. 40 shows one of 

 these cases. These two groups may possibly be cases of second- 

 ary fragmentation. Occasionally as in Fig. 30, A (PI. XIII.), the 

 nuclei arising by fragmentation are unusually large and perhaps 



