FISHES 159 



cyclopean eye that was used by the ancient amphibians, 

 and resembles a small eye in a certain living reptile in 

 New Zealand. The more we examine the anatomy of 

 the animals, the more rudimentary organs we discover. 

 In the whale the pelvis and hind-limbs remain as 

 shrunken relics buried in the flesh ; and amongst the 

 serpents there are species that still show rudiments 

 of the pelvis. 



In the case of many of these organs the reduction is 

 due to natural selection, which has a much greater 

 significance in this direction than most experts admit. 

 But it does not explain every case ; above all, we can 

 only understand with its aid how an organ can be 

 reduced to a body that is indifferent for the life- 

 purposes of an organism. We have already spoken of 

 those island-dwelling insects that have had their wings 

 reduced to small relics, because those that could fly well 

 were too frequently carried by the wind into the sea. 

 In this case natural selection had to reduce the wings 

 until the insects could not raise themselves with them 

 any longer. There its function ceased. It could not 

 make the wings any smaller, because if no insect could 

 fly any longer, there was no ground for selection, and 

 for the function of flight the sole cause of selection it 

 was a matter of complete indifference whether or no 

 the wings were reduced by another fraction of an inch. 



There are also insects in Europe that never fly. 

 These are the females of most of the bombycidae. 

 When they emerge from the pupa-covering, they remain 

 in the same spot, and are sought and fertilised by the 

 active males, and then lay their eggs. The reason for 



