466 THE HISTORY OF BIOLOGY 



Whatever their view of life, the species idea was to them essentially a prac- 

 tical basis for comparative morphology, whereas the problem of creation 

 was a question that was entirely put aside as not concerning natural science. It 

 must at once be admitted that it was certainly due to Darwin's dilettante 

 conception of nature that he thus adopted just the problem of creation as 

 a starting-point for many years of research work and cogitation; on the 

 other hand, it was his treatment of the problem that caused such a public 

 sensation over his work. 



Immutability and creation 

 LiNN^us in his youth defined the species as the progeny of those animals 

 that had been created in the beginning; he afterwards altered his view, in 

 that he assumed a few species to have been created, out of which the others 

 were evolved at a later period. To the systematists who succeeded him it 

 was the immutability of the species that was the essential point, the actual 

 basis of the system, while the problem of creation was seldom discussed. 

 De CandoUe, it will be remembered, has a definition of species based on 

 mutual similarity and fertility between the individuals, but without any 

 mention's being made of the creation. To Darwin, however, "immutable" 

 and "created," in regard to species, are inseparable terms; doubt of the im- 

 mutability of the species is induced by doubt of the creation, which in its 

 turn has been caused by the species' conditions of distribution and not by 

 any doubts as to the assumption of a supernatural act of creation being in 

 itself an explanation of nature.^ Then he gets the idea of the variations 

 which by means of natural selection are adapted to prevailing external con- 

 ditions, thus giving rise to, first of all, new varieties, and then new species. 

 Even earlier systematists had taken it for granted that varieties are produced 

 by external conditions, flourish, and disappear; what is novel in Darwin's 

 theory is that the species are nothing but more fully developed varieties, 

 which selection, resulting from the struggle for existence, has determined, 

 while the intermediary varieties, as being less capable of defying competi- 

 tion, have perished. He adduces a great many arguments to prove that those 

 species which are most widely scattered and, where they exist, are richest 

 in individuals are also those which produce the most varieties, which in 

 his view is the same as initial species. And he points out how vague the 

 boundaries between species and varieties really are in the minds of different 

 systematists and how difficult it is to define what is meant by species. He 

 considers that this name is given arbitrarily and for the sake of convenience 

 to a number of individuals which highly resemble one another, and that it 



^ In his diary of the voyage Darwin in one place explains the absence of certain fossils 

 in a geological deposit by assuming that animals of that kind had not been created at the time 

 when the deposit came into being (Life and Letters, II, p. i). Again, in the Origin of Species a 

 Creator is mentioned as the ultimate cause of life. 



