116 NATURAL SCIENCE [August 
yet a quite unproven principle.” The “contention” of the paper 
is that there is no proof forthcoming of man’s greater variability. 
Whether either sex is the more variable is left for the future to 
settle in the following words :— 
“When more material is available, and finer methods are 
applied, then perhaps it will be possible to detect a more note- 
worthy preponderance of variability in the one or other sex.” 
And, again, in referring to the slight preponderance of variability 
observed in woman :—“ TI strongly suspect that this preponderating 
variability of women is mainly due to a relatively less severe 
struggle for existence.’ These are not the words of one whose 
“object is to support the contention that women are, on the whole, 
more variable than men.” They seem to me the words of one who 
wishes to reach a scientific conclusion without any party or sex 
bias. 
In the next place, Professor Weldon objects to my use of the 
co-efficient of variation. He apparently wishes to assert that 
absolute variation is the real test of most things. I am some- 
what surprised to see him advocating this test. It is not so 
many months since an American critic pointed out how fatally 
this measurement of variation affected the conclusions of a certain 
paper of Professor Weldon’s on selective mortality in crabs. I 
have not seen any answer to that criticism, and I very much doubt 
if one can be found. Some years ago I pointed out to him that 
the same measurement of variability led to absurd results in the 
case of the selective mortality of men. 
But even here Professor Weldon puts in my mouth opinions I 
have never expressed. He writes:—“The violent assertion that 
there is only one ‘scientific’ measure of variability is therefore to 
be regretted.” Now, so far from asserting the validity of only one 
measure of variability, I carefully state in paragraph (c) of my 
conclusions :— 
“There is more than one method of quantitatively measuring 
variability, but the measure which is really significant for pro- 
gressive evolution has not hitherto been determined.” 
On p. 343 I write, ‘“‘ We may stay to ask whether the statistics 
of skull capacity do not in themselves give us any information with ~ 
regard to the superiority of either standard deviation or the co- 
efficient of variation as a test of that variability which is valuable 
for progressive evolution,” and on p. 345 I conclude that the 
results do not enable us to say offhand that absolute or percentage 
variation is a better measure of the variability which is a source 
of progressive evolution. These are hardly the words of one who 
has made a “violent assertion that there is only one measure of 
variability.” 
