SYNAPSIS AND CHROMOSOME ORGANIZATION 487 



with one end at the proxinaal pole of the nucleus and the other 

 end separating distally into two single threads — was clearly 

 seen for a number of those represented and indicated for the 

 others. The deeply staining body near the accessory (X) is 

 regarded as the supernumerary chromosome. In this stage in 

 this material none of the atelomitic chromosomes could be iden- 

 tified and, while the tendency for conjugation to begin at the 

 proximal ends of the threads is clearly indicated, the behavior 

 of the atelomitic chromosomes could not be followed. 



d. Chromatid movements. Differences in rates of development, 

 or progress toward separation at anaphase, in different cells 

 find some striking examples in the series drawn on plate 2. 

 Chromosome number 1 seems to be lagging somewhat behind 

 the others in cells B and C, though in cell D it is as far advanced 

 as any. In cell D, number 2 is not so far along toward its 

 typical metaphase condition as it is in cell C. The same rela- 

 tions appear to hold for chromosome 5 in these two cells, yet 

 all of the chromosomes in cell D are more condensed and there- 

 fore presumably nearer metaphase than they are in cell C. 



In the metaphase there are also some striking differences. 

 Number 4 in cell G is very far behind the other members of the 

 complex and seemingly little advanced in chromatid movement 

 beyond the condition seen in cell A. In cell F, too, separation is 

 not so far advanced for this chromosome as it is in cell E. Cell H 

 is in early anaphase, and cells E, F, and G are at about the 

 same metaphase stage, yet chromosome 9 is not so far advanced 

 toward complete separation in F as it is in E, and in E it is not 

 so far along as in G, yet in G it seems further along than in H. 

 Again number 6 is lagging in cells F and G, as compared to the 

 conditions in E and H. The examples of this chromosome in 

 cells F and G are at about the same stage, but in G a ring exists 

 through the contact of the ends of the arms at the right which 

 are seen to be free in cell F. 



All these differences seem to indicate that the extent of chro- 

 matid movement is variable, not only for different chromosomes 

 but also for the same chromosome in different cells, so that in 

 some cases the movement which ends in the separation accom- 



