140 D. H. WENRICH 



hand, there is some evidence of division of these granules, as 

 seen, for instance, in figure 8. Here the long row seems to be 

 double in the distal part and the two rows appear to lie close 

 together. The distance between them is foreshortened, how- 

 ever, in this position. The duplication in connection with the 

 short row behind the nucleus is difficult to interpret, and I am 

 not sure that division of the granules is indicated. 



B. Metaphase 



Figures 22 to 26 show a series which includes a very late 

 prophase or early metaphase (fig. 22), metaphases, and early 

 anaphases, which indicate very well the behavior of the chromo- 

 somes in these stages. In figure 22 the chromosomes are still 

 similar to those of the earlier prophases, the two parts of each 

 being closely approximated with their long axes parallel. Al- 

 though the fibers of the forming spindle have already become 

 attached to the chromosomes, the latter have not as yet lined 

 up into a definite plate. It appears from these figures that 

 whatever directive influence the spindle fibers may have in the 

 separation of the chromosomes, it is exercised for some of them 

 before the plate has become established. All the figures with an 

 equatorial plate show the two parts of some of the chromosomes 

 already drawn out so that they are in contact only at their ends, 

 while others are just in the process of being separated. Since 

 I have seen a great many animals in the stage indicated bj^ figures 

 23, 24, and 25 and none showing stages between them and figure 

 22, I judge that some of the chromosomes are separated during 

 the formation of the metaphase plate. 



As seen in the figures mentioned, the number of chromosomes 

 in the metaphase is definitely six, the number found in the 

 prophases. Martin and Robertson ('11) and Kuczynski ('14, 

 '18), as previously noted, believe that eight(?) prophase chromo- 

 somes are reduced to four multiple elements in the metaphase. 

 I think I have demonstrated the probability that the prophase 

 number in Kuczynski's figures is six, and the tendency for the 

 metaphase chromosomes to clump probably accounts for the 

 apparent number, four. Kofoid and Swezy ('15) do not show 



