THE ORIGIN OF SPECIES 511 



explained by the present unless good cause can be shown to the contrary; and 

 the fact that, so far as our knowledge of the past history of life on our globe 

 goes, no such cause can be shown — I can not but believe that Lyell was, for 

 others, as for myself, the chief agent in smoothing the road for Darwin. For 

 consistent uniformitarianism postulates evolution as much in the organic as 

 the inorganic world. The origin of a new species by other than ordinary 

 agencies would be a vastly greater " catastrophe " than any of those which 

 Lyell successfully eliminated from sober geological speculation. 17 



But however much Lyell may have " smoothed the road," Huxley, 

 and most of the biologists of those thirty years, declined to go in 

 thereat. It remained for an anonymous amateur, whom they there- 

 upon with one accord fell to abusing, to point out the practicability of 

 that highway. In the " Vestiges " and the " Explanations " Chambers 

 urged the presumption from geological uniformitarianism with an ef- 

 fective use of concrete examples. 18 



If there is anything more than another impressed on our minds by the 

 course of geological history, it is that the same laws and conditions of nature 

 now apparent to us have existed throughout the whole time. Admitting that 

 we do not now see any such fact as the production of new species, we at least 

 know that, while such facts were occurring upon earth, there were associated 

 phenomena of a perfectly ordinary character. For example, when the earth 

 received its first fishes, sandstone and limestone were forming in the manner 

 exemplified a few years ago in the ingenious experiments of Sir James Hall. 

 ... It was about the time of the first mammals that the forest of the Dirt Bed 

 was sinking in natural ruin amidst the sea sludges, as the forests of the Plan- 

 tagenets have been doing for several centuries upon the coast of England. In 

 short, all the common operations of the physical world were going on in their 

 usual simplicity, obeying the laws which we now see governing them; while the 

 supposed extraordinary causes were in requisition for the development of the 

 animal and vegetable kingdoms. There surely hence arises a strong presumption 

 against any such causes. 



It is a curious circumstance, however, that the argument from uni- 

 formitarianism cut both ways. As Wallace says: 



One of the greatest, or perhaps we may say the greatest, of all the diffi- 

 culties in the way of accepting the theory of natural selection as a complete 

 explanation of the origin of species, has been the remarkable difference between 

 varieties and species with respect to fertility when crossed. 19 



This difference, as Darwin said in the " Origin," seemed, on the face 

 of it, " to make a broad and clear distinction between varieties and 

 species." And the apparent existence of such a radical distinction 

 between the varieties produced under domestication and true physio- 

 logical species was an objection, not only against natural selection, but 

 also against evolution itself; for it meant that we do not see now, nor 

 within the limits of human observation, organisms actually getting 



17 " Life and Letters of Charles Darwin," Ch. XIV. The letter to Lyell is 

 in " Life and Letters of Thomas Henry Huxley," I., 174. 



18 " Vestiges," reprint in " Morley's Universal Library," 1890, p. 114. 



19 " Darwinism," p. 152. 



