184 CHARLES L. PARMENTER 



representing the relative positions of the two groups and figure 

 25 B shows the chromosomes enlarged and numbered consecu- 

 tively. As in case 3, the two groups are not immediately 

 adjacent, but are separated by the longer diameter of a resting 

 nucleus. 



In group a there are eleven chromosomes. In the other group 

 there are apparently seventeen, but unfortunately in this second 

 group the chromosomes are so overlapped at one point that 

 they cannot be counted with confidence. There are, however, 

 thirteen chromosomes which can be clearly delineated and the 

 interpretation that there are four chromosomes in the group 

 (14 to 17) which so badly overlap is likely correct. The total 

 number of chromosomes in the two groups is then probably 

 twenty-eight. 



The chromosomes are so much foreshortened, and at the 

 above-mentioned point so crowded, that I have not attempted to 

 measure and arrange them in a series as was done for the chro- 

 mosomes of figures 24 and 26. However, a glance at figure 25 B 

 shows that such a series might be arranged. 



The shape and size of both groups of chromosomes, and of 

 the cytoplasm about them, are such that one can be fitted upon 

 the other. Although these two relations are not positive evidence 

 they indicate that one of these groups, possibly the smaller, has 

 been separated from the other. 



To summarize, it may be said that in the first case considered 

 (fig. 22) it is certain that the smaller number of chromosomes is 

 due to a loss of a part of the chromosome complex from the cell. 

 Although the facts stated for cases 2, 3, and 4 may not be con- 

 sidered absolute proof, they do constitute a very strong prob- 

 ability, which closely approximates a proof, that in each of these 

 cases a cell has been separated into two parts. 



B. Somatic chromosome pairs 



a. Introductory statement. Since Van Beneden's ('83) hj^^oth- 

 esis that one-half of the chromosomes of an individual are of 

 paternal origin and that one-half are of maternal origin there 



