Mimetic Patterns to the Original Form. 77 
my conviction, formed after much deliberation, of the 
gradual and natural character of these complicated 
changes, and of the absence of any violent or arbitrary 
element in their process of development. Whether 
the explanations here suggested are true and adequate, 
can in most instances only be decided by observation in 
the field; and it is much to be desired that travellers and 
residents in countries where these and similar phenomena 
occur should carefully record all facts relating to the 
habits, postures, modes and times of flight, prevalence, 
seasonal occurrence and exact distribution of the various 
species that come under their observation. 
There is also need of such experimental evidence as to 
the means of defence adopted by these forms as can only 
be satisfactorily obtained in the midst of their natural 
surroundings. Meanwhile, it must suffice to point out 
the conclusion towards which the only facts available 
appear to lead, while the actual verification by observa- 
tion and experiment must perforce be left to those whose 
opportunities enable them to apply these final tests to the 
subjects of enquiry. 
My best thanks are due to Prof. Poulton, F.R.S., for 
much encouragement and many facilities for work. ‘he 
figures were drawn, by his permission, from specimens in 
the Hope Collection at Oxford. 
