CHAP. xxi. THEORY OF 6 CREATION BY VARIATION.' 417 



nance having already begun to change. To many, this doc 

 trine of Natural Selection, or 'the preservation of favoured 

 races in the struggle for life,' seems so simple, when once 

 clearly stated, and so consonant with known facts and 

 received principles, that they have difficulty in conceiving 

 how it can constitute a great step in the progress of science. 

 Such is often the case with important discoveries, but in 

 order to assure ourselves that the doctrine was by no means 

 obvious, we have only to refer back to the writings of skilful 

 naturalists who attempted in the earlier part of the nine 

 teenth century, to theorise on this subject, before the inven 

 tion of this new method of explaining how certain forms 

 are supplanted by new ones, and in what manner these 

 last are selected out of innumerable varieties, and rendered 

 permanent. 



Dr. Hooker, on the Theory of ' Creation by Variation ' as 

 applied to'the Vegetable Kingdom. 



Of Dr. Hooker, whom I have often cited in this chapter, 

 Mr. Darwin has spoken in the Introduction to his ( Origin of 

 Species,' as one f who had, for fifteen years, aided him in every 

 possible way, by his large stores of knowledge, and his excel 

 lent judgement.' This distinguished botanist published his 

 ' Introductory Essay to the Flora of Australia ' * in 1859, the 

 year after the memoir on ( Natural Selection 'was communi 

 cated to the Linnsean Society, and a few months before 

 the appearance of the f Origin of Species.' 



Having, in the course of his extensive travels, studied the 

 botany of arctic, temperate, and tropical regions, and writ 

 ten on the flora of India, which he had examined at all 

 heights above the sea, from the plains of Bengal to the limits 



* Introductory Essay, &c., sold separately. Loyell Eeeve, London, 1859. 



E E 



