214 Robertson: Theories of Evolution. 
with his compeers, and so will be most likely to leave offspring” 
Further, the brilliant plumage and beautiful song of some male 
birds is attributed to a more peaceful rivalry in which the birds 
compete for the favour of the female, displaying before 
her their plumage and their voice. The female is said in 
such cases to actually select the most attractive male. Wallace 
is in entire disagreement with Darwin as to the possibility of 
the plumage and song of the cock bird being evolved in response 
to the taste of the hen. He thinks that where the male has 
gayer plumage than the female this simply means that the need 
for protection represses in the female the bright colours which 
are normally produced in both sexes by general laws. He also 
believes that brightness of colour is correlated with vigour, 
and hence the male exceeds the female in brilliancy owing to his 
higher vigour and vitality. It further follows from this 
correlation that the more vigorous males which succeed best in 
the struggle for the female will be the most brilliant, and hence 
vividness of colour will be selected incidentally by the ‘law of 
battle.’ 
Numerous criticisms of the theory of Natural Selection have 
been brought forward from time to time. The most serious 
collection of difficulties in the way of theory is probably that 
brought together by Darwin himself in the ‘Origin of Species,’ 
for his intense intellectual honesty made him state all possible 
drawbacks to this theory in a more forcible and telling way 
than his opponents could! Perhaps there is no more cogent 
difficulty than that of accounting for the zzczpient stages of useful 
modifications. Many adaptations, which are obviously useful 
when highly developed, do not seem likely to have been of any 
advantage to the creature in their rudimentary stages. A second 
difficulty of a slightly different type is that of the wdzlity of 
specific differences. On Darwin's theory utility is the sole test 
by which a variation stands or falls, but in many cases the very 
constant differences distinguishing two allied species have, so 
far as we can judge, no utility whatever. In Mr. Bateson’s 
words :—‘as to the particular benefit which one dull moth 
enjoys as the result of his own particular pattern of dulness as 
compared with the closely similar pattern of the next species, 
no suggestion is made.’ 
These difficulties are very real, and they show us that the 
‘Origin of Species,’ magnificent as it is, ought not to be accepted 
as the last word on the subject. Darwin himself (unlike some 
modern ‘ Darwinians!’) never looked upon Natural Selection as 
Naturalist, 
