LINNEAN SOCIETY OE LONDON. XIU 



professes to bo, to endeavour to cast a slur on the observations of 

 some of our most accurate botanists and zoologists, by representing 

 them as " tinged vrith Darwinism ;" and on the other hand, I scarcely 

 think that due allowance is made for those who, like myself, througii 

 a long course of study of the phenomena of organic life, had been 

 led more and more to believe in the immutability of species within 

 certain limits, and have now felt their theories rudely shaken by the 

 new light opened on the field by Mr. Darwin, but who cannot sur- 

 render at discretion so long as many important outworks remain 

 contestable. Difference of opinion and eagerness of support of op- 

 posite theories act as a great incentive to the investigation of hidden 

 facts, and thus promote the cause of science, but only so long as they 

 are carried on without personalities and without dogmatism on the 

 one hand or virulence on the other. Although, therefore, we cannot 

 allow the time of our own meetings nor the pages of our publication 

 to be devoted to the abstract discussion of any such theories, yet we 

 should give every encouragement to the search after facts, on the one 

 side or on the other, irrespective of what we may deem extravagant 

 in the results which might be deduced from them. 



Passing over the purely speculative part of the subject, as to how 

 the first species or series of species originated, which appears to me 

 to be utterly beyond human comprehension, and which, whatever 

 theory we adopt, we must believe without material evidence, I take 

 it to be generally admitted that, pre\T.ous to the races of Hving beings, 

 animal or vegetable, which now cover our globe, it was inhabited by 

 animals and plants, as numerous, perhaps,^and in many respects as 

 diversified as those of the present day, but totally distinct from them 

 as to species, and that the real question is how the one has been re- 

 placed by the other. 



The extinction of ancient races is comparatively easy of compre- 

 hension. We all see how species gradually disappear from particular 

 districts, and how many are becoming exceedingly rare in any 

 country ; and we have at least the Dodo amongst animals, and the 

 St. Helena Trochetias amongst plants, which are now believed to be 

 totally extinct, although we have specimens prepared from the life 

 during the short time which has elapsed since natural-history collec- 

 tions were first formed. The discussion as to whether the majority of 

 ancient species have disappeared by a similar gradual extinction, or 

 by sudden convulsions, belongs more to geologists than to ourselves. 

 But of the commencement of any one species we have no human 

 record, and, as far as naturalists are concerned, we must rely en- 

 tirely on cuxumstautial evidence. 



