Evidences of Theory of Natural Selection. 289 



cast-off shell of a mollusk; because the shell was 

 primarily of use to the mollusk itself, and, so far as the 

 mollusk is concerned, the fact of its shell being after- 

 wards of a secondary use to the crab is quite immaterial. 

 What Darwin's challenge requires is, that some structure 

 or instinct should be shown which is not merely of such 

 secondary or accidental benefit to another species, but 

 clearly adapted to the needs of that other species in the 

 first instance such, for example, as would be the case 

 if the tail of a rattle-snake were of no use to its 

 possessor, while serving to warn other animals of the 

 proximity of a dangerous creature ; or, in the case of 

 instincts, if it were true that a pilot-fish accompanies a 

 shark for the purpose of helping the shark to discover 

 food. Both these instances have been alleged ; but 

 both have been shown untenable. And so it has 

 proved of all the other cases which thus far have been 

 put forward. 



Perhaps the most remarkable of all the allegations 

 which ever have been put forward in this connexion 

 are those that were current with regard to instincts 

 before the publication of Darwin's work. These 

 allegations are the most remarkable, because they 

 serve to show, in a degree which I do not believe 

 could be shown anywhere else, the warping power 

 of preconceived ideas. A short time ago I happened 

 to come across the 8th edition of the Encyclopaedia 

 Britannicci) and turned up the article on " Instinct " 

 there, in order to see what amount of change had been 

 wrought with regard to our views on this subject by 

 the work of Darwin the hth edition of the Encyclo- 

 paedia Britannica having been published shortly before 

 The Origin of Species by means of Natural Selection. 



* U 



