182 
CHARLES L. PARMENTER 
Della Valle (’09, p. 117)' claims that variation of chromosome 
number is probably a general law and (p. 120) that his counts 
strikingly bear out the expectation expressed by Newton’s theo¬ 
retical binomial curve. Were this the condition in Ambystoma 
tigrinum, a good proportion of the sixty-six complexes should 
have shown variation in number. Since no variation was found, 
it is safe to conclude that there is none in the cells that could 
not be counted. 
c. Abnormal complexes. Seven apparent variations from the 
usual number were found. These were groups of chromosomes 
in which the number was clearly other than twenty-eight (figs. 
22, 24, 25, A.B., 26, A.B.). But when these groups are thoroughly 
analyzed it is certain that they are nothing else than cases of a 
very unusual behavior of four cells and do not constitute a 
variation from the usual number of chromosomes. 
Figure 22 shows a peritoneal cell which has lost a part of the 
chromosomes. Chromosome a is but part of a chromosome, 
showing very unmistakable evidence that a portion of it has been 
broken off and there is a conspicuous depression in the tissue 
from which it is evident that the remainder of the chromosomes 
of this cell have been lost. The cell lies close to a tear in the 
peritoneum. It is a bare possibility that the tear and the loss 
of the chromosomes is due to the same cause. 
The second case is a very early metaphase from the peritoneum. 
It consists, as represented in figure 24, of one group of twelve 
chromosomes and another group of sixteen immediately adja¬ 
cent to it. These two groups and figures 2 and 20 are very 
similar to Della Valle’s dicentric cell (’09, fig. 6) and Flemming’s 
(’91) figures 31 to 39, table 40. A study of these two groups 
makes it practically certain that they are separated parts of one 
and the same cell. This is evidenced by the following facts: 1) 
these two groups together constitute the normal number twenty- 
eight. 2) The chromosomes of both groups of cells are in the 
same stage of mitosis. 3) Both groups represent a half circle 
and indicate strongly that they are separated parts of one cell 
wdiich have rotated a total of 180° to their present positions. 4) 
When these chromosomes are arranged side by side linearly they 
