7592 Notices of New Books. 



different measure, of any individual, how is it that every organic indi- 

 vidual around us does not bear the impress of the process of change, 

 and repudiate specific clanship ? To account for this Mr. Darwin 

 introduces several principles — "the struggle for existence," just 

 referred to; "variation under nature;" "natural selection;" "ex- 

 tinction;" " divergence of character;" and " correlation of growth." 

 These are all treated of under several distinct heads, but they appear 

 so intimately connected that in the following short summary we must 

 consider them together. First, then, the struggle for existence is the 

 generation of a greater number of individuals than can be supported ; 

 and this, again, is parallel with the production of a greater number of 

 species than the divided functions of nature are ordained for. Then 

 comes the assumed fact of variation under nature, deduced from the 

 evidence of variation under domestication. Variation under nature is 

 primarily the slight difference of individuals, parallel also with the 

 slight difference of sets of individuals. Slight differences involving 

 slight advantages in the struggle for existence, some must give way ; 

 these advantages, however infinitely slight, turn the scale in favour of 

 the possessors. Then follows extinction on the death of the weaker 

 individuals, and parallel with it also, in a variety of grades, the 

 extinction of sets of individuals, or specific groups, by stronger sets 

 of individuals encroaching upon them. Divergence of character, or 

 the production of individuality in species, results in the struggle for 

 existence taking place, as it were in separate little groups, by the 

 most closely related individuals striving for an identical part of the 

 sphere of nature ; and as the individuals having the character suiting 

 them for that sphere most strongly developed would obviously gain 

 the mastery, the less characteristic individuals of each little group of 

 competition will be extinguished, and the conquerors consequently be 

 placed in a more isolated position. Then, the different groups will 

 perhaps vary in their power of reproduction and persistency, and as 

 they extend will encroach upon and compete with each other, some 

 becoming extinguished, and others of stronger power will thus become 

 still further isolated, and, again dividing and subdividing by newly- 

 developed grades of character, fill a disproportionate share of the 

 arena of nature ; and thus Mr. Darwin accounts for the apparent want 

 of symmetry in the measures of difference separating genera and species. 

 The theory is certainly very plausible, and presents an easy means 

 of accounting for the irregular grades of difference observable in the 

 organic series. The general completeness of the series, and the 

 apparently irregular gaps that here and there occur, impress the mind 



