610 CAROLINE M. HOLT 



to Dr. Stevens' view that we have here three bivalent chromo- 

 somes — the same condition found by Metz ('14) in Drosophila, 

 where parasynaptic union of homologous chromosomes takes 

 place between mitoses. Fance ('17) has demonstrated that the 

 normal somatic number may, by improved technique, be clearly 

 shown to be six. 



The four normal complexes shown in figure 21, a, b, c, and d, 

 may be interpreted in two ways. 21 d seems to represent an 

 early metaphase before the final equatorial arrangement and 

 di\dsion of bivalent chromosomes, while a, b, and c may be 

 groups in which homologous bivalent chromosomes are separat- 

 ing and are about to pass to the poles; in fact in a, they are 

 already moving away from the center. Under such an interpre- 

 tation, the six chromosomes in a, b, and c, are in each case, 

 bivalent, representing fused homologous elements. The enlarged 

 ends, which not infrequently are split, suggest such a condition. 

 The other interpretation of these four groups is that each of 

 the six chromosomes in a, b, and c is a univalent chromosome, 

 lying in the equatorial plate, ready for division. The work of 

 other investigators indicates that the latter is the true interpre- 

 tation. As in normal somatic cells, homologous chromosomes 

 tend to fuse during the resting stage; so in the metamorphosing 

 gut cells, the same condition apparently obtains. 



In Culex, the degenerating intestinal cells frequently show 

 thirty-six or forty-eight elements; and in one case, at least 

 sixty-eight chromosomes appear in a metaphase group. This 

 particular cell probably contains seventy-two, although it is 

 not possible to determine the exact number (fig. 23, y and ^). 

 But whatever the number, approximately four divisions of half 

 of each of the original chromosomes must here be represented, 

 and three of the other half. 



It is possible that cytokinesis does not always follow karyo- 

 kinesis, though there may be an increase in the amount of cyto- 

 plasm, since some of the cells containing multiple complexes are 

 larger than the normal (fig, 8). But, if this be the case, we 

 might expect to find multinucleated cells, and there is no evi- 

 dence of such a condition, save in a few possible instances where 



