CHROMOSOME NUMBER AND PAIRS IN AMBYSTOMA 201 



of the chromatic elements are directly comparable to the size 

 and number of the fluid crystals which are formed in a solution 

 under different conditions. 



These contentions he supports with the claim ('09) of a 

 variation of nineteen to twenty-seven chromosomes in forty 

 mitoses of the peritoneum, and ('11) by a very large variation 

 in the blood cells of fe'alamandra maculosa. These observations 

 he supplements with a long list of citations of chromosome num- 

 bers which he interprets as supporting his contention. 



But, following an apparently frank and critical discussion of 

 the accuracy of his observations in the peritoneal cells, he says 

 ('09, p. 116) that he is only sure of his enumeration in twenty- 

 five of the forty cells discussed. These twenty-five complexes 

 he describes as being very clear. The range of variation in these 

 cells is as follows: 



Number of chromosomes. 



Number of mitoses 



Number of mitoses 



An examination of his descriptions and figures may indicate to 

 some extent the reliability of these counts. 



His count of 22 chromosomes was made upon a polar view of 

 a very late anaphase (fig. 2) in which he states the smaller chro- 

 mosomes in the center of the complex w^ere beginning to go to 

 pieces and becoming indistinct, and his only doubt is whether 

 the chromosome numbered 18 is one or two chromosomes. But, 

 judging from similar stages in my material, it seems to me that 

 where the chromosomes are beginning to go to pieces in as 

 crowded a condition as this must be, such a complex is not a 

 safe object for an exact chromosome count. 



Instances of this kind make it seem possible that conditions 

 which he considers clear for an exact count might be much less 

 conclusively clear to others, and that his drawings do not represent 

 the actual conditions in his complexes. 



Since his citations of chromosome number variations found in 

 the literature have been discussed by Montgomery ('10), Wilson 

 ('10), and by McClung ('17, p. 548 ff.), it is not necessary to 



