On the Relation of, Mimetic Characters to the Original Form. 
By F?*A. Dixey, M.A., M.D., Fellow of Wadham 
College, Oxford. 
(Abstract.) 
An objection that has been often brought against the 
theory of mimicry, as enunciated by Bates and accepted 
by Darwin, is the difficulty of imagining the first stages 
in the production of a mimetic pattern. Fritz Miiller* 
endeavoured to meet this objection by alleging that mimicry 
chiefly originated between forms that already bore consider- 
able resemblance to each other. The main instance (that 
of Leptalis melia) on which he relied in order to prove his 
point was not well chosen, for there is reason to think that 
he was in error both in considering that this species repre- 
sented the ancestral form of Leftalis and in supposing that 
it was not protected by mimicry. Nevertheless his conten- 
tion is sound in so far as it emphasises the fact that the 
process of mimetic assimilation depends rather on the de- 
velopment of old than on the starting of new features. 
An illustration of this principle is afforded by a com- 
parison of the non-mimetic butterflies Previs locusta and 
P. thaloe with the mimetic species of the closely allied genus 
Mylothris, and with Heliconius numata, which serves as the 
model for the latter; all these forms inhabiting the same part 
of the neotropical region. An almost perfect transition can be 
traced on the undersides from the non-mimetic species of 
Pieris through M. lypera 3, M. lorena 3, M. pyrrha 3, M. 
lorena 2, to M. pyrrha Q, this last butterfly being a very close 
copy of Heliconius numata. The whole series shows (1) that a 
practically perfect mimetic pattern can be evolved by gradual 
and easy stages without any violence or abruptness of 
change; (2) that it 1s not necessary that the forms between 
which mimicry originates should possess considerable initial 
resemblance ; (3) that so small a beginning as the basal red 
* Jenaisch. Zeitschr., vol. x., 1876. 
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