CONCLUSION 323 



from time to time, each at a single step, from pre- 

 existing species. Upon the material thus supplied 

 natural selection operates ; the weaker go to the wall, 

 the stronger survive. This is also, in all probability, 

 the way in which adaptations have arisen. Creatures 

 'vhich came into existence displaying a particular new 

 structure, which happened to be fitted for a particular 

 new function or suited to a particular niche in Nature, 

 survived and flourished exceedingly. Those in which 

 undesirable organs appeared perished and were no 

 more seen. To take Aristotle's example. If a man 

 were to be born with molars in front and incisors at 

 the back of his jaw he would die a.t least, in the days 

 before dentistry. Having his teeth in the positians 

 in which they actually stand (although not for this 

 reason only), he survives and rules the world. 



After all, the difference between the point of view 

 thus briefly indicated, and that of Darwin as expressed 

 in the c Origin of Species,' is only one of detail of 

 detail as to the particular sort of variations by which 

 evolution chiefly proceeds. Darwin's analogy between 

 the origin of species in Nature and the origin of races 

 under cultivation may be repeated with emphasis, 

 although Huxley's famous criticism, to the effect that 

 races which are sterile together have not arisen in 

 cultivation, is not yet completely answered. But 

 this renders the discontinuous origin of such sterility 

 only the more likely ; and when we recall the Mendelian 

 behaviour of such characters as long and short style in 

 the primrose, or sterility of the anthers in the sweet- 

 pea, the solution of the problem does not seem very 

 far to seek. 



