chap, vin.] PROTECTIVE RESEMBLANCES. 207 



that it is almost impossible at first not to believe that 

 fungi have grown on the butterflies themselves ! 



If such an extraordinary adaptation as this stood alone, 

 it would be very difficult to offer any explanation of it ; but 

 although it is perhaps the most perfect case of protective 

 imitation known, there are hundreds of similar resem- 

 blances in nature, and from these it is possible to deduce 

 a general theory of the manner in which they have been 

 slowly brought about. The principle of variation and that 

 of " natural selection," or survival of the fittest, as elabo- 

 rated by Mr. Darwin in his celebrated " Origin of Species," 

 offers the foundation for such a theory; and I have myself 

 endeavoured to apply it to all the chief cases of imitation 

 in an article published in the Westminster Review for 1867, 

 entitled, " Mimicry, and other Protective Resemblances 

 among Animals," to which any reader is referred who 

 wishes to know more about this subject. 



In Sumatra, monkeys are very abundant, and at Lobo 

 Raman they used to frequent the trees which overhang 

 the guard-house, and give me a fine opportunity of 

 observing their gambols. Two species of Semnopithecus 

 were most plentiful — monkeys of a slender form, with very 

 long tails. Not being much shot at they are rather bold, 

 and remain qiiite unconcerned when natives alone are 

 present ; but when I came out to look at them, they would 

 stare for a minute or two and then make off. They take 



