Criticisms of Theory of Natural Selection. 355 



that a wing could be of no conceivable use until it had 

 already acquired enormous proportional dimensions, 

 as well as an immense amount of special elaboration 

 as to its general form, size of muscle, amount of blood- 

 supply, and so on. For, obviously, not until it had 

 attained all these things could it even begin to raise 

 the animal in the air. But observe how fallacious is 

 this argument. Although it is perfectly true that a 

 wing could be of no use as a wing until sufficiently 

 developed to serve the purpose of flight, this is merely 

 to say that until it has become a wing it is no use as 

 a wing. It does not, however, follow that on this 

 account it was of no prior use for any other purpose. 

 The first modifications of the fore-limb which ended 

 in its becoming an organ of flight may very well have 

 been due to adapting it as an organ for increased 

 rapidity of locomotion of other kinds whether on 

 land as in the case of its now degenerated form in the 

 ostrich, or in water as in the case of the expanded fins 

 of fish. Indeed, we may see the actual process of 

 transition from the one function to the other in the 

 case of " flying-fish." Here the progressive expansion 

 of the pectoral fins must certainly have been always 

 of use for continuously promoting rapidity of loco- 

 motion through water ; and thus natural selection 

 may have continuously increased their development 

 until they now begin to serve also as wings for carry- 

 ing the animal a short distance through air. Again, 

 in the case of the so-called flying squirrels we find the 

 limbs united to the body by means of large extensions 

 of the skin, so that when jumping from one tree to 

 another the animal is able to sustain itself through a 

 long distance in the air by merely spreading out its 

 A a 2 



