282 RECAPITULATION. [Chap. XV. 



great classes, which has prevailed throughout all time. 

 This grand fact of the grouping of all organic beings 

 under what is called the Natural System, is utterly in- 

 explicable on the theory of creation. 



As natural selection acts solely by accumulating 

 slight, successive, favourable variations, it can produce 

 no great or sudden modifications; it can act only by short 

 and slow steps. Hence, the canon of " Natura non f acit 

 saltum," which every fresh addition to our knowledge 

 tends to confirm, is on this theory intelligible. We can 

 see why throughout nature the same general end is 

 gained by an almost infinite diversity of means, for 

 every peculiarity when once acquired is long inherited, 

 and structures already modified in many different ways 

 have to be adapted for the same general purpose. We 

 can, in short, see why nature is prodigal in variety, 

 though niggard in innovation. But why this should be 

 a law of nature if each species has been independently 

 created no man can explain. 



Many other facts are, as it seems to me, explicable on 

 this theory. How strange it is that a bird, under the 

 form of a woodpecker, should prey on insects on the 

 ground; that upland geese which rarely or never swim, 

 should possess webbed feet; that a thrush-like bird 

 should dive and feed on sub-aquatic insects; and that a 

 petrel should have the habits and structure fitting it for 

 the life of an auk ! and so in endless other cases. But 

 on the view of each species constantly trying to increase 

 in number, with natural selection always ready to adapt 

 the slowly varying descendants of each to any unoccu- 

 pied or ill-occupied place in nature, these facts cease to 

 be strange, or might even have been anticipated. 



We can to a certain extent understand how it is that 



