IX 

 MIMICRY AND NATURAL SELECTION 



The English Address to the Fifth International Zoological Congress 

 held at Berlin. Read at the ' Allgemeine Sitzung ', August 15, 1901. 

 Reprinted from Verhandl. d. V. Internal, Zool. Congr. z. Berlin, Jena, 

 1902, p. 171. 



Revised: an Appendix added. 



I FEEL it to be a great honour and pleasure to be called 

 on to deliver the address on behalf of the English-speaking 

 nations to the Fifth International Zoological Congress, 

 at Berlin. At the same time I am sensible of the great 

 difficulty of the task, in the attempt to say anything ade- 

 quate on so wide a subject in the narrow compass of 

 five and forty minutes. 



In attempting to arrive at a decision upon the origin 

 and cause of Mimetic Resemblance we have no direct 

 evidence to assist us. We are driven to base our opinion 

 upon the same ground as that upon which the belief in 

 the theory of Gravitation is founded. This theory finds 

 acceptance, not because of direct evidence in its favour, 

 but because the facts of the Cosmos, so far as we know 

 them, are consistent with the theory and none of them 

 inconsistent with it. 



It is necessary therefore first to give a brief account of 

 the theories which have been advanced to explain the 

 origin of Mimicry, secondly to inquire how far each one 

 of them is consistent with the main facts of Mimicry. 



i. The Theory of Natural Selection as an explanation, 

 assumes that these resemblances have been produced 

 because they are or have been useful in the struggle for 

 existence. There has been, according to this interpreta- 

 tion, a greater average survival in successive generations 

 of the forms in which these useful likenesses were more 



