VALIDITY OF SOME FORMS OF MIMICRY. 697 



natural selection, but beyond this some are not prepared to go. 

 Others believe more or less implicitly in cryptic mimiciy, either 

 active or passive, and that peculiar form of it known as Batesian 

 mimicry, that is, the resemblance for protection of a palatable to 

 an unpalatable species. And there are others again who, believing 

 in these, consider that Miillerian mimicry, that is, the resemblance 

 of unpalatable species for mutual protection brought about by the 

 tasting experiments of young reptiles and birds, plays a veiy 

 large part, even an overwhelming one, in the production of 

 mimicry. 



The theories of the two great naturalists Bates and M idler 

 have now been before us for a great number of years ; but both, 

 the latter more especially, base their claims to recognition on 

 indirect evidence and not on experiments and investigation in the 

 field. The exponents of these two theories maintain that though 

 direct evidence is largely absent, yet on no other reasonable 

 hypothesis can these remarkable cases of mimicry be explained. 

 The opponents, on the other hand, hold the view that as direct 

 evidence is possible though admittedly difficult to obtain, it ought 

 to be produced before either theory can be admitted as proved, 

 and until it is forthcoming they remain either actively hostile or 

 passively sceptical. It was with the feeling that both the sup- 

 porters of these theories and those opposed to them were equally 

 desirous of reaching some finality in this vexed question, which has 

 now been before them in one form or other for half a century — a 

 question which, with its periodical exhibition of violent eruption 

 and deceptiv^e quiescence much resembles an Iceland geyser — that 

 I have duinng the past five yeai^s devoted as much of my time as 

 was practicable to the study of insectivorous birds and reptiles ; 

 and I have taken as my areas of investigation the islands of 

 Bourbon, Mauritius, and Ceylon, because the question is less 

 complicated on an island of small or moderate dimensions than on 

 such an extensive area as Africa or South America. 



Before I left England in 1908 I had the great advantage 

 of being taken over the National Collection of Butterflies by 

 Mr. Guy Marshal], who, with his unrivalled knowledge of the 

 subject and persuasive powers, almost then and there made me 

 throw in my lot with the supporters of the Miillerian theory, but 

 in the midst of his arguments recollections of scenes in tropica] 

 jungles ol^truded themselves, and I was left in an irritating 

 condition of mingled belief and incredulity. A fairly extensive 

 reading of the whole subject consequently did little to convince 

 me, and my personal bearing towards both Batesian and Miillerian 

 mimicry was that the verdict must be the unsatisfactory one of 

 " not proven." 



I propose taking each of the islands in tui'n, enumerating the 

 reptiles and birds with their habits and distribution, directing 

 attention to the more striking cases of mimicry, and endeavouring 

 to ascertain on such data how far these theories are negatived or 

 sustained. 



