510 VniversUij of California. Publications in Zoology [Vol. 20 



(fig. 7) and finally take their positions at the ends of the spindle, form- 

 ing the polar caps or centrosomes (pi. 44, fig. 9). They are still con- 

 nected by the darkly staining line which appears to lie in close prox- 

 imity to the inner face of the nuclear membrane. During the time 

 that the centrosomes are taking their position at either margin of the 

 nuclear membrane, the granules of the dispersed karj-osome and the 

 dark gray region around them undergo a complete readjustment, out 

 of which emerges a characteristic spindle upon which are arranged 

 the chromosomes in a late propha.se (fig. 8). During this process the 

 linin network disappears and the nucleus becomes elongated (fig. 9). 

 Wenyon (1907) stated that there did not appear to be a formation of 

 definite chromosomes, but from the present study it appears that six 

 chromatin masses are arranged on the spindle (pi. 44, fig. 8), and the 

 conclusion is that these are the chromosomes. C. fuuris thus differs 

 from C. lafleuri, which has eight chromosomes (Kofoid and Swezy, 

 1921), but agrees with E. coli, which also has six (Swezy, 1922). 



Metaphase. — The separation of the chromosomes on the spindle to 

 form the metaphase is not always synchronous. In plate 44, figure 9, 

 the two upper chromosomes appear in the metaphase, while the lower 

 chromosomes have already divided and the daughter chromosomes are 

 beginning to separate. This non-synchronous division of chromosomes 

 is also illustrated in the lower nucleus (pi. 44, fig. 14) in which some of 

 the daughter chromosomes have nearly reached the polar caps, while 

 two are still in the middle of the spindle. 



The chromosomes appear as small granules, some representing 

 spheres, while the others are somewhat elongated. There is evidence 

 that of the six chromosomes in this species, two are large ellipsoids, 

 two are small spheres, and the other two are slightly elongated and 

 midway between the other pair in size (pi. 44, figs. 12, 17). 



Anaphase. — After the division of the chromosomes in the meta- 

 phase there is an immediate pulling apart of the daughter chromo- 

 somes toward either end of the spindle as is shown in the lower nucleus 

 (pi. 44, fig. 13) and the upper nucleus (fig. 14). This separation is 

 accompanied b.y a disappearance of the spindle fibers between the 

 separating daughter chromosomes and by a further elongation of the 

 nucleus (pi. 43, fig. 13, lower nucleus). The intradesmose also becomes 

 fainter in the median region and a complete separation of the polar 

 caps ensues as the intradesmose retracts or fades away. 



Telophase. — As good figures of this phase have been particularly 

 rare, it is concluded that the final separation into two nuclei is com- 



