194 c - M - CHILD. 



containing irregular strands and masses of chromatin as if in 

 preparation for a division were formed about the periphery of a 

 cytophore (Fig. 24, PL XL). These were very probably stages 

 following the first spermatocytic division. 



Fig. 25 (PI. XII.) shows the metaphase of the second sperma- 

 tocytic division in a group cytophore. Here again the divisions 

 are more or less nearly tangential. Fig. 26 (PI. XII.) shows the 

 anaphase in a portion of a group. 



V. The Fragmentation of Spermatocyte Nuclei. 



In Section III. (pp. 181-182) it was stated that certain of the 

 nuclei of the first spermatocytes become larger than the others, and 

 that the spireme instead of becoming more dense and giving 

 rise to chromosomes becomes less dense and very irregular 

 and the nucleolus remains instead of disappearing (Fig. 13, 

 B, PI. X.). These nuclei constitute the earliest recognizable 

 stage in a remarkable process of fragmentation which is appar- 

 ently a normal phenomenon in the testes of both species of Mon- 

 iezia. The process is so entirely different from anything de- 

 scribed in the spermatogenesis of other forms that at first I 

 regarded it as a form of degeneration. But repeated examina- 

 tion of old and new material during four successive years has 

 convinced me that the process gives rise to nuclei which are in- 

 distinguishable from the spermatid nuclei which have arisen by 

 mitosis. Whether these "spermatid nuclei" resulting from the 

 fragmentation of spermatocyte nuclei actually take part in the 

 formation of functional spermatozoa it is impossible to determine, 

 but that spermatozoa structurally similar to those developing 

 from nuclei which arise in the ordinary manner develop from 

 these spermatids is, as will appear probable. 



This process, like the typical spermatogenesis, occurs in iso- 

 lated cells or simultaneously in groups. In the latter case the 

 different members of the group fuse together, in the manner de- 

 scribed in the preceding section, and this cytoplasm forms a 

 cytophore. It is rare, however, that groups so regular in form 

 and arrangement as that shown in Fig. 27, A (PI. XII.), are found 

 More commonly only two or three cells fuse together or the 

 process occurs in isolated cells. Fig. 27, A (PI. XII.) shows a 



