NATURAL SELECTION V. ADAPTATION. 



71 



NATURAL SELECTION VEBSUS ADAPTATION ; OR, 

 DARWINISM AND EVOLUTION. 



By Rev. Prof. G. Henslow, M.A., V.M.H., &c. 



Part I. — Natural Selection. 



In 1839 Darwin first sketched out his ideas of Evolution, and in 1844 

 laid them before Sir (then Dr.) J. D. Hooker and Sir Charles Lyall. 

 The paper consisted of two parts. The first part dealt with " The Varia- 

 tion of Organic Beings under Domestication and in their Natural State " ; 

 the second part formed the paper read before the Linnean Society on 

 July 1, 1858, entitled " On the Variation of Organic Beings in a State of 

 Nature ; on the Natural Means of Selection ; on the Comparison of 

 Domestic Races and true Species." 



On the same occasion a paper by Mr. A. R. Wallace was read, " On 

 the Tendency of Varieties to depart indefinitely from the Original Type." 



In both papers Evolution by the aid of Natural Selection is really the 

 subject ; but while Darwin based his theory on the study of animals 

 and plants under domestication, Wallace maintained that " no influences 

 as to varieties in a state of nature can be deduced from the observation of 

 those occurring among domestic animals. The two are so much opposed 

 to each other in every circumstance of their existence that what applies 

 to one is almost sure not to apply to the other." * 



Darwin was first led to entertain ideas of evolution by his studies of 

 the extinct and existing fauna of South America and elsewhere in his 

 voyage round the world in the "Beagle," and it is the great merit of his 

 labours that they put before the world that great doctrine in a more 

 presentable and acceptable form than had been previously done. He was 

 far from being the first to believe in or describe it. One of the most 

 important of his predecessors was Lamarck ; but that observer introduced 

 a hypothetical element, which rather damaged the acceptance of his theory, 

 namely, the element of volition on the part of animals in acquiring new 

 forms of structure ; and attributing a power to the environment of being 

 an actual cause of producing the change in the organism. 



W T e shall see, however, that we are fast returning to " Lamarckism," 

 with the omission of its untenable elements. 



Darwin took his idea of " natural selection " from Malthus' "Essay on 

 Population," published near the end of the eighteenth century. Wallace 

 appears to have derived his from nature itself. But both utilised the 

 " struggle for existence " which occurs everywhere in nature, partly in 

 consequence of so many more offspring being born annually than can 

 possibly survive ; partly in consequence of overcrowding by other kinds of 

 plants ; partly by an inhospitable environment, enemies, ill luck, &c. But 

 the origin of specific characters depends upon alterations of form, and not 



* Journ. Linn. Soc. 1858, p. 61. 



