LINNEAK SOCIETY OF LONDON. XV 



by authority. It has been supported by observations so numerous 

 in every branch of natural history, that, when assailed, it has only 

 been thought necessary summarily to refute any theories that may 

 have been raised in opposition to it. This was an easy task so long 

 as those theories were confined to mere speculations ; and even now 

 that the plausible application of undeniable facts to the establish- 

 ment of serious objections, or at any rate of important exceptions, has 

 caused a revolution in the views of many eminent naturalists, there 

 are others who still more or less maintain the unity and original 

 independence of existing species. 



The third hypothesis, that the present species are lineally descended 

 from preexisting ones by a process of gradual variation, was gene- 

 rally treated as an idle speculation, and, whenever brought forward, 

 only broached to be almost unanimously rejected, until the publica- 

 tion of Mr. Dar^sdn's ' Origin of Species.' This remarkable work 

 has carried more or less of conviction into such minds as those of 

 Lyell, Hooker, A. Gray, A. DeCandolle, and others whose previous 

 arguments pointed towards a contrary direction ; it has met with the 

 most cordial adoption on the part of many eminent men who had 

 not so committed themselves, and has excited in a large proportion 

 of other naturalists doubts as to their previous firmest convictions. 

 This has been effected rather by the extreme simplicity of the new 

 principle applied to phenomena previously observed, but little attended 

 to, and now first placed in juxtaposition, than by the discovery of 

 any remarkable hitherto hidden phenomenon. By connecting the 

 hereditary diversities in constitution as well as in form in the 

 oflfepring of a species, with the premature destruction from external 

 causes of the immense majority of the offspiing produced, and by 

 siipposing that permanence would be given to those varieties alone 

 whose hereditary constitution is the best suited to resist or survive 

 these causes of destruction, Mr. Darwin has shown how specific 

 changes may take place ; and by the accumxilation of a vast number 

 of carefully observed or weU-autheuticated facts, aided by great 

 lucidity of exposition and powers of argument, he has endeavoured 

 to show how they do take place. His is not therefore a theory 

 capable of proof, but " an unimpeachable example of a legitimate 

 hypothesis " requiring verification, as defined by J. S. Mill in his 

 excellent chapter on Hj-pothesis, commencing the second volume of 

 his Logic, Mr. Darwin has proceeded with this verification so far 

 as the present state of our knowledge permits ; and we must, I think, 

 cordially agree with the same distinguished logician, that he has 

 " opened a path of inquiry full of promise, the results of which no 



