220 president's address. 



result of long-continued tliouglit and labour, directed by a natu- 

 ralist of extended attainments and remarkable ability, to consoli- 

 date a theory wliich has some facts on which to rest. Some of 

 his postulates we must allow. All organic beings are liable to 

 vary in some degree, and tend to transmit such variations to their 

 offspring. All, at the same time, tend to increase at a very rapid 

 rate, and their increase is kept in check by the incessant compe- 

 tition of other individuals of the same species, or that of indivi- 

 duals of other species, or by injurious physicial conditions. 

 Whatever variation occurs among the individuals of any species 

 of animals or plants which is advantageous for their existence, 

 will give these individuals an advantage over their fellows, and 

 will be probably inherited by their offspring. It is thus that 

 Mr. Darwin assumes all species to have originated. 



I feel tempted to say a few words on this, especially, as before 

 the publication of Mr. Darwin's work, I had expressed this 

 opinion in a paper published in the " Ibis," as to many species 

 of birds which I should rather term local varieties. But Mr. Darwin 

 maintains that the distinction between species and varieties is 

 an arbitrary one ; and he challenges his opponents to say wherein 

 the difference consists. That many naturalists, the Germans 

 especially, have needlessly multiplied species, I freely own; and, 

 moreover, that we frequently apply the term species, for conve- 

 nience sake, to forms which, at the same time, we are perfectly 

 aware are in reality only varieties. But yet I humbly conceive that 

 the distinction may be a very real one, though we may not always 

 be able to draw the line. Has Mr. Darwin forgotten the old 

 fallacy of the last straw which breaks the camel's back ? And 

 yet we know there is such a thing as an overload. Our author, 

 in a somewhat triumphant tone, quotes the instance of the grouse, 

 and alleges the difference of opinion among naturalists as to the 

 specific distinction between Scotch and willow grouse. But here, 

 I believe, no sound naturalist would assert a specific distinction, 

 though the local races be different. Generally speaking, I con- 

 ceive that there would be no difficulty in the differentiation of 

 species, as an hereditary organism, distinguishable from all others, 

 which either will not hybridize, or of which the hybrids are 



