202 
CHARLES L. PARMENTER. 
review them extensively. But Della Valle’s attitude and his 
conception of what constitutes clearness and certainty may be 
better understood in the light of some of these citations of 
chromosome variations, especially in the Amphibia, which he 
presents as valid evidence of variation in chromosome number. 
He quotes (’09, p. 35) Flemming (’81, [’82] p. 51) and Rabl 
(’84, [’85] p. 248 to 250) as reporting variations of from seventeen 
to twenty-four in the gill epithelium of Salamandra maculosa. 
Flemming explicitly states (pp. 51 and 52) that in the three 
cells which admit an exact count there are twenty-four chromo¬ 
somes, that in about twenty other cells he counted from seven¬ 
teen to twenty-four, but was not certain of the number, and 
assumed that there were twenty-four. Rabl says (’85, p. 248) 
that up to that time only eleven unquestionable counts had been 
made and each of them showed twenty-four chromosomes. In 
no exact counts in any cell had a different number been found. 
Della Valle seems to think that Torok’s (’88) figures of erythro¬ 
cytes of Salamandra maculosa show a variation. This work 
was not concerned with chromosome number and the figures 
were not intended to show the number of chromosomes in the 
cell. His citations of the work of Carnoy and Lebrun (’00) on 
Rana temporaria, and of Lebrun (’02) on Diemyctylus and Bom- 
binator may be criticised because the authors were primarily 
concerned with other considerations and only gave approximate 
number determinations. Winiwarter (’00, p. 699), as cited by 
Della Valle, reports a variation of chromosome number in the 
rabbit; but he states that he is uncertain of his counts. The 
variations reported by Barratt (’07, p. 376), in proliferating 
epithelium of the rabbit are in pathological tissue, and, more¬ 
over, his counts are uncertain. Montgomery (’10) has shown 
that many other such citations are misinterpreted. 
The above cases represent Della Valle’s inexact and uncritical 
attitude in relation to data that seem to serve his purpose, and 
this creates the suspicion that his attitude interfered with the 
accuracy of his observations when he counted the chromosomes 
in his own material. This suspicion approaches a probability 
in view of the fact that numerous competent investigators who 
