BLACKMAN. — SPERMATOGENESIS OF THE MYRIAPODS. 495 



somes, still in the form of granular segments, are in contact with the 

 forming karyosphere and very plainly are about to undergo a similar 

 process. This disposition of the chromosomes around the accessory 

 chromosome continues (Figure 5) until all of them are aggregated in 

 one irregular densely staining mass, the karyosphere (Figures 6, 7). 



In Scolopendra heros it was never possible to establish conclusively 

 that the chromatin enters the karyosphere as definite individual chromo- 

 somes. That this is the case was, however, ahvays believed by the 

 author, and indeed there was considerable evidence supporting this 

 view. In Scolopendra subspinipes more convincing evidence was found, 

 as the nucleolar material there present serves as a background against 

 which the chromosomes can be seen in favorable cases. However, some 

 doubt might still remain. 



The stages in the formation of the karyosphere in Lithobius mordax 

 furnish better evidence of the individuality of the chromosomes during 

 the early spermatocytic stages than those of any other myriapod yet 

 studied. It can be very plainly seen that the chromosomes enter into 

 the formation of the karyosphere as distinct ekments tvithoitt losing their 

 individuality. Evidences of this fact are found at all stages in the 

 formation of the karyosphere in the irregular lobulated structure of 

 this body (Figures 5-8). Each one of these lobules undoubtedly repre- 

 sents a chromatin segment which has become shortened and thickened 

 into an irregularly rounded body. In Figure 5 several of these chromo- 

 somes still remain detached from the rest and their identity is easily 

 recognized. In Figure 6 the individuality of many of the elements 

 may still be readily seen, while in Figure 7 the grouping of the 

 chromosomes is but little closer. 



Shortly after the stage shown in Figure 7, the karyosphere begins 

 to undergo a change by which the dense mass of chromosomes is con- 

 verted into the completely formed karyosphere of the vesicle stage. 

 This change consists in the acquisition of a large amount of nucleolar 

 material. This results in three changes in the appearance of the 

 karyosphere. The first two of these are changes in size and shape, by 

 which the irregular lobulated karyosphere of the young spermatocytes 

 is converted into the larger spherical body characteristic of the vesicle 

 stage. The presence of nucleolar material in the karyosphere also 

 brings about a change in its staining reactions. 



In Figure 8 is seen an early stage in this metamorphosis. By com- 

 paring the karyosphere in this cell with that shown in Figure 7, the 

 changes mentioned above are immediately apparent. The karyosphere 

 has undergone a considerable increase in size and a portion of the 

 surface has assumed a regular rounded outline. The portion of the 



