THE SPERMATOGENESIS OF THE MYRIAPODS. 



193 



tocytes to that of the spermatogonium stands in a ratio of ten to 

 one. 



Striking as this great increase in the size of the cells certainly 

 is, it is not as remarkable as are the changes which occur in the 

 cell in general and especially in the nucleus. Shortly after the 

 formation of the nuclear membrane, the chromatin segments 

 leave the tangled mass at one side of the nucleus (Fig. 5), and 

 arrange themselves irregularly throughout the nuclear space 

 (Fig. 6). At the same time they shorten and thicken and, as the 

 nucleus is now quite large, the individual elements may readily be 

 distinguished and their number counted. In all favorable cases 



FIG. 8. X I >44 dia. Pseudo-germinal vesicle stage of the spermatocyte of Sco- 

 lopendra heros. Chromatin all aggregated in karyosphere which here plainly shows ex- 

 cept at one point a spongy or reticular structure. This dense portion undoubtedly 

 represents the accessory chromosome. Persisting spindle still visible. Centrosomes 

 to be seen imbedded in the zone of archoplasm surrounding the nucleus. 



in which this count has been taken it has been found that there 

 are seventeen chromosomes present (sixteen granular segments 

 and the accessory chromosome), the number later found in the 

 metaphase. At this time (Fig. 6) the cells resemble insect 

 spermatocytes more closely than at any other stage. They are 

 now in a condition apparently comparable in all particulars to 

 that of the ordinary sperm cell in the "segmented spireme " 



