THE CAUSE OF MIMETIC RESEMBLA>'CE. 603 



enormous number of observed facts in all parts of the world. I 

 believe that the generalizations will be admitted to be sound 

 and to be well warranted by the facts. Under any theory wliich 

 is not based upon selection, the whole of tbe facts on which 

 the generalizations rest become mere coincidences and receive 

 no explanation of any kind. Under natural selection this vast 

 body of facts becomes at once intelligible. Here the accu- 

 mulated facts of the most diverse kind, which receive an intelli- 

 gible explanation by the theory in question, yield a firm support 

 to the theory. There are many theories wliich are held upon 

 indirect evidence of precisely the same nature. We believe in 

 evolution, not because we see it taking place, but because 

 of the immense number of observed facts which it renders 

 intelligible. 



In the case of natural selection in relation to mimicry aud 

 common warning colours it is to be confidently hoped that direct 

 evidence may yet be added ; indeed, a considerable amount is even 

 now forthcoming. Prof. Lloyd Morgan's recent work upon the 

 activities and instincts of young birds of many species (' Habit 

 and Instinct,' London, 1896) proves that their education is 

 actually of the kind which is presupposed in the theories of 

 H. W. Bates and Fritz Muller. He shows that they have no 

 instinctive knowledge of things which are good for food, but 

 examine and test everything. On the other hand, they have very 

 retentive memories, and retain a firm impression of the appear- 

 ance of objects which have given them an unpleasant experience. 

 Furthermore, there was evidence that they are influenced in 

 their behaviour towards other objects resembling the one 

 which has proved objectionable to them. As to the aggressive 

 Hymenoptera, the evidence of their special methods of defence 

 is obvious to everyone. With regard to specially protected 

 groups of butterflies there is a large amount of evidence from 

 observation and experiment, but more is to be desired. As 

 this paper is going through the press I have received the last of 

 Mr. Frank Finn's interesting and important set of papers on this 

 question (Journal, Asiatic Society of Bengal, Ixiv. pt. ii. 1895, 

 p. 344 ; Ixv. pt. ii. 1896, p. 42 ; Ixvi. pt. ii. 1897, p. 528 ; Ixvii. 

 pt. ii. 1897, p. 614). After a long series of experiments begun 

 and conducted with a perfectly open mind, upon Indian insect- 

 eating vertebrates, Mr. Finn concludes in favour of the theories 

 based upon natural selection in the following words : — 



