286 Darwin, and after Darwin. 



of water-weed which had been introduced from 

 America, that considerable expense had to be incurred 

 in order to clear the river for traffic. In New Zealand 

 the same thing has happened with the European 

 water-cress, and in Australia with the common rabbit. 

 So it is doubtless true, as one of the natives is said to 

 have philosophically remarked, " the white man's rat 

 has driven away our rat, the European fly drives away 

 our fly, his clover kills our grass, and so will the Maoris 

 disappear before the white man himself." Innumer- 

 able other cases to the same effect might be quoted ; 

 and they all go to establish the fact that forms less 

 fitted to survive succumb in their competition with 

 forms better fitted. 



Secondly, there is a general consideration of the 

 largest possible significance in the present connexion 

 namely, that among all the millions of structures and 

 instincts which are so invariably, and for the most part 

 so wonderfully, adapted to the needs of the species 

 presenting them, we cannot find a single instance, 

 either in the vegetable or animal kingdom, of a 

 structure or an instinct which is developed for the 

 exclusive benefit of another species. Now this great 

 and general fact is to my mind a fact of the most 

 enormous, not to say overwhelming, significance. The 

 theory of natural selection has now been before the 

 world for more than thirty years, and during that time 

 it had stood a fire of criticism such as was never en- 

 countered by any scientific theory before. From the 

 first Darwin invited this criticism to adduce any single 

 instance, either in the vegetable or animal kingdom, of 

 a structure or an instinct which should unquestionably 



