CHROMOSOME NUMBER AND PAIRS IN AMBYSTOMA 203 



have made extended and careful studies of the germmal and 

 somatic mitoses of the same species mention no variation in 

 chromosome number. Furthermore, Meves ('11), who attacks 

 the theory of individuahty, fails to substantiate Delia Yalle's 

 observations, and it is not at all likely that he would have failed 

 to mention any variation observed. He appears to believe (p. 

 296) that the number is constant. However, Heidenhain ('07, 

 p. 176, figs. 80 and 81) shows a polar view of a late prophase 

 and a lateral view of a metaphase with twenty-six and twenty- 

 two chromosomes, respectively, and states that such irregu- 

 larities occasionally occur. An occasional variation is not sur- 

 prising, but variations as numerous as Delia Valle claims to be 

 present are unusual. Flemming ('90, p. 78) states that he 

 observes in the lungs of Salamandra maculosa numerous atypical 

 mitoses with very short chromosomes. He gives no further 

 discussion and no figures to indicate what kind of cells they are 

 nor whether they are normal. In the ten cells of the lung of 

 Amby stoma tigrinum (table, p. 177) there were no variations in 

 chromosome number, and with the exception shown in figure 26 

 I observed no abnormalities. Delia Valle's ('11) figures of blood 

 cells in Salamandra maculosa, which he claims show an extreme 

 variation in chromosome number, appear very much like cells 

 undergoing disintegration. 



To the above evidence of the questionableness of Delia Yalle's 

 results may be added the results of the sixty-six counts in Amby- 

 stoma tigrinum showing no variation in number. The important 

 fact that these counts were made wdth extreme care (p. 177) in 

 the somatic cells of the same and other tissues of a closely related 

 species, and made in uncut membranes (which Delia Valle 

 emphasizes as important for accurate counts), further strengthens 

 the already strong probability that his number determinations 

 are incorrect. 



There are certain characteristics in his figures that also indicate 

 that his drawings are none too accurate. He notices that the 

 chromosomes are twisted, but he does not show what constitutes 

 the twist. That the peritoneal chromosomes of Salamandra 

 maculosa are each composed of two separate chromatids twisted 



