182 CHARLES L. PARMENTER 



Delia Valle ('09, p. 117) claims that variation of chromosome 

 rmmber 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 of!" 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 Delia Valle's dicentric cell ('09, fig. 6) and Flenmiing'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 

 which have rotated a total of ISO'' to their present positions. 4) 

 When these chromosomes are arranged side by side linearly they 



