XV VARIATION AND EVOLUTION 177 



genus Euralia belonging to the entirely different 

 family of the Nymphalidae, to which there is no 

 evidence for assigning the disagreeable properties of 

 the Danaines. Now the different species of Euralia 

 show remarkably close resemblances to the species 

 of' Amauris, which are found flying in the same 

 region, and it is supposed that by " mimicking " the 

 unpalatable forms they impose upon their enemies 

 and thereby acquire immunity from attack. The 

 point at issue is the way in which this seemingly 

 purposeful resemblance has been brought about. 



One of the species of Euralia occurs in two very 

 distinct forms (PI. VII.) which were previously re- 

 garded as separate species under the names E. 

 wahlbergi and E. mima.. These two forms respec- 

 tively resemble Amauris dominicanus and A. echeria. 

 For purposes of argument we will assume that one of 

 these forms has been derived from the other and that 

 A. dominicanus is the more recent form of the two. 

 On the modern Darwinian view certain individuals 

 of A. echeria gradually diverged from the echeria type 

 and eventually reached the dominicanus type, though 

 why this should have happened does not appear to 

 be clear. At the same time those specimens of the 

 Euralia which tended to vary in the direction of A. 

 dominicanus in places where this species was more 

 abundant than A. echeria were encouraged by natural 

 selection, and under its guiding hand the form wahl- 

 bergi eventually arose from mima. 



According to Mendelian views, on the other hand, 

 the dominicanus pattern arose suddenly from the 

 echeria pattern (or vice versa), and similarly wahl- 

 bergi arose suddenly from mima. If wahlbergi 



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