16 MIMICRY— [ch. 



the less abundant species the gain would of course be 

 relatively greater. Theoretically therefore, all of the 

 five species would profit if in place of five distinct 

 warning patterns they exhibited but a single one in 

 common. And since it is profitable to all concerned 

 what more natural than that it should be brought 

 about by natural selection ? 



Midler's views are now widely accepted by students 

 of mimicry as an explanation of these curious cases 

 where two or more evidently distasteful species closely 

 resemble one another. Indeed the tendency in recent 

 years has been to see Miillerian mimicry everywhere, 

 and many of the instances which were long regarded 

 as simple Batesian cases have now been relegated to 

 this category. The hypothesis is, of course, based upon 

 what appears to man to be the natural behaviour 

 of young birds under certain conditions. No one 

 knows whether young birds actually do behave in the 

 way that they are supposed to. In the absence of 

 any such body of facts the Miillerian hypothesis ./ 

 cannot rank as more than a plausible suggestion, and, 

 as will appear later, it is open to severe criticism on 

 general grounds. 



Perhaps the next contribution to the subject of 

 mimicry which must rank of the first importance was 

 that of Erich Haase 1 , to whose book students of these 

 matters must always be under a heavy obligation. 

 It was the first and still remains the chief work of 

 general scope. Since Haase' s day great numbers of 



1 Uniersuchungen iiber die Mimikry, 1893. 



