XV 
THE RELATION OF FACTS TO THEORIES 325 
Criticism of Other Theories 
Theories which attempt to minimise Natural 
Selection seem always sooner or later to assume 
an inheritance of acquired characters, and of this 
there is little evidence. They also assume that 
environmental influences have a direct effect upon 
the organism, and of this Weismann’s work has 
made many doubtful. Or rather, Weismann has 
endeavoured to prove that those apparently direct 
responses to environmental stimuli which are facts 
of experience, can be interpreted also as the result 
of adaptation, and this, if proved, is fatal to 
theories like that of Simroth. It is, however, 
to be noticed that in the case of the artificially 
produced variations in the colours of butterflies, 
competent entomologists (e.g. Garbowski) are of 
opinion that the new colours have little or no phylo¬ 
genetic importance, and that as yet it is impossible 
to correctly interpret them. There is, indeed, much 
evidence to show that in the case of butterflies the 
colours can be influenced by their surroundings in a 
way of which the mechanism is at present unknown. 
Much of this is, however, apart from our main 
object, which is merely to show that in spite of the 
fluency with which so many people talk of the 
meaning of colour in organisms, the subject is as in¬ 
complete on the theoretical as on the physiological 
side. It seems reasonable to believe that the two 
deficiencies are related, and that a little more 
physiology will arm the theorists with better 
weapons. In the meantime, we cannot end a book on 
Colour more fitly than by an appeal for more facts. 
