( xxiv ) 



one, it supplies the strongest possible proof of the reality of 

 mimicry and of the power of natural selection to produce it — 

 indeed, it is a crucial test." 



To pass over this challenge in silence would convey the 

 wholly false impression that his arguments are unanswerable, 

 and that Miillerian Mimicry is at last firmly established on 

 its pedestal. I therefore propose to examine closely this 

 " crucial test," and shall show that far from being conclusive 

 of mimicry it affords the " strongest possible proof " of its 

 inherent unsoundness. 



Though our Society rightly refuses to open its pages to 

 controversy, yet when an opportunity arises for settling once 

 for all by means of scientific investigations the validity or 

 otherwise of a theory which has been before us in one form 

 or other for over half a century, and which has obtained a world- 

 wide celebrity, such opportunity should not be lost. 



The crucial test Dr. Carpenter brings forward is briefly as 

 follows : — Immediately off the north-west coast of the 

 Victoria Nyanza lies a small archipelago known as the Sesse 

 Islands, the largest of which is Bugalla, distant from the 

 mainland near Entebbe about twenty-five miles. 



The nearest of the Sesse Islands is, I believe, within sight of 

 the mainland. 



On Bugalla and also on Damba Island to the N.E. of the 

 Sesse group, the species Pseudacraea eurylus f. kobleyi is 

 abundant, and shows great diversity of marking, so much so 

 that many of the varieties have received distinctive names and 

 are regarded as transitional forms resembling the genus 

 Planema. For some reason, probably the absence of the food- 

 plant, Planema is distinctly rare on the island, though very 

 abundant in the neighbourhood of Entebbe on the mainland, 

 where also Pseudacraea occurs equally commonly; but (and 

 this is the important point) transitional forms are absent or 

 very rare. (Whether Pseudacraea is regarded as an edible 

 genus or not, is not stated, and for our purpose is immaterial.) 



The argument to account for the absence of these transitional 

 forms is best given in Dr. Carpenter's own words. 



" Now on the Island it is quite conceivable that an enemy 

 of the Pseudacraea might never see Planema at all : at any 



