CHAP. XXI. THEORY OF "CREATION BY VARIATION." 417 



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

 trine of Nutui-al Selection, or "the presei'vation of favored 

 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 imj)ortant discoveries, but, in 

 order to assure ourselves that the doctrine was by no mean.s 

 obvious, we have onl}^ to refer back to the writings of skilful 

 naturalists who attempted, in the earlier part of the nine- 

 teenth century^ to theorize 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. 



Br. Hooker on the Theory of " Creation by Variation" as 

 applied to the Vegetable Kingdom. 



Of Dr. Hooker, whom I have often cited in this chaj)ter, 

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

 Species," as one "who had, for fifteen years, aided him in 

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

 excellent judgment." This distinguished botanist published 

 his " Introductory Essay to the Flora of Australia"* in 1859, 

 the year after the memoir on " Natural Selection" was com- 

 municated to the Linniean Society, and a few months before 

 the appearance of the " 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. Lovell Keeve, London, 1S59. 



