226 SCIENCE PROGRESS 



therium, one need hardly expect to be able to demonstrate any 

 perceptible change by experiments in a human life-time. Nor 

 are we able to say how the offspring can be influenced. But 

 we do say that the evidence is quite conclusive that it is 

 influenced. 



In the evolutionary series of the horse we see the gradual 

 increase in size of the middle toe and the gradual dwindling 

 of the side toes. It has been very plausibly argued that the 

 middle toe has increased through nature favouring those forms 

 in which it is better developed, and less plausibly argued that 

 the side toes have dwindled and become lost through nature 

 eliminating those types in which the side toes proved a slight 

 handicap as against others in which the side toes were even 

 more reduced. But if we consider all the change that has taken 

 place in 1,000,000 generations it will readily be seen that at 

 no time has nature ever anything very tangible to select. 

 And as we have the clearest evidence that certain changes 

 could not have been produced by natural selection we are 

 probably justified in doubting if any have been. 



It is well known that underground and cave-dwelling 

 animals have usually small eyes or have entirely lost their 

 eyesight. We cannot of course demonstrate an evolutionary 

 series showing all the stages by which the eyesight has become 

 lost in Notoryctes or Chrysochloris . But by examining other 

 animals of somewhat similar habit we see various stages in the 

 reduction of the eye such as may have been passed through. 

 In Georychus the eye is small ; in Talpa it is still more reduced. 

 In Chrysochloris it is quite under the skin and pretty certainly 

 functionless. In Notoryctes only a rudiment is left. The old 

 natural selection arguments brought forward to account for 

 the reduction of the eye of the mole are seen to be of no value 

 when we consider the problem of the further reduction of the 

 functionless rudiment of the eye deep below the skin. 



In all the divisions of the vertebrates we have examples 

 of increased development with increased function and reduced 

 development with lessened function. But one of the most 

 striking examples is the reduction in size of the wing in birds 

 which have ceased to fly. It matters not whether the bird is 

 a rail, a pigeon, or a goose, if it takes up its abode on an island 

 where it is free from ground enemies it no longer requires to 

 fly, and as a result of its gradually ceasing to use its powers of 



