CHAPTER XX 



THE ORIGIN OF SPECIES 



No subject in biology has been the cause of such excited debate 

 and controversy as has this, since the pubHcation of Darwin's 

 Origin of Species in 1859. Were it not that Age and Area seems 

 to have some not unimportant bearings upon the subject, we 

 should not bring into this book so thorny a matter of dispute. 



If in this chapter or elsewhere I seem severely to criticise the 

 Darwinian theory, it is not because I do not appreciate its many 

 strong points, nor is it that I am trying to throw contempt upon 

 it. The theory is as legitimate a subject for criticism as is any 

 other. It does not seem to me that it has been properly realised 

 that the "Darwinian theory" has two separate sides. Darwin's 

 immortal service to science lies in the fact that he established 

 the theory of E^'olution— until then regarded with contempt— 

 in an unshakeable position, which all subsequent research has 

 only strengthened. But to establish it he had to invent some 

 machinery by means of which it might be supposed to work, and 

 for this purpose he devised the very simple and beautiful mechan- 

 ism of natural selection. So strong was the a jniori evidence in 

 favour of this, and so well did natural selection seem to explain 

 almost everything in animated nature, that within a short time 

 it was accepted all round, and with it the theory of evolution, 

 which is now established as the rider of thought, not only in the 

 scientific world, but outside of it. The mechanism of natural 

 selection has, however, been for a long time subject to an in- 

 creasing severity of criticism, and as a working theory is now 

 becoming largely moribund. 



No theory as yet brought forward in biology has been for so 

 long a time a stimulant to research, nor has any proved so 

 fruitful in educing valuable work. It may suffice to call attention 

 to the very different position of biology in 1859, and at the 

 present time. It is hardly too much to say that all, or nearly 

 all, the work done during that time owes its incejition, at least, 

 to the influence of the Darwinian theory. Not only so, but it 

 has produced the most far-reaching effects in all branches of 

 human thought. 



The literature in praise of the theory is already very bulky, 



