166 GENERAL DISCUSSION [ch. xiv 



as it was in daily life, it was assumed to be a competition of 

 groups. Whatever may be the case with animals, there seems 

 little or no reason to imagine that plants compete as groups. It 

 is this assumption which has become so marked a feature in 

 social and political life — that the best, and incidentally the most 

 satisfactory, solution of a difficulty or of a competition lies in 

 the conquest and dominance, or even in the extermination, of the 

 opponent. Species, to begin with, are not structural units with 

 all individuals just alike, any more than are language groups of 

 mankind. The nearest approach to this condition is in such cases 

 as Coleus elongatus (p. 24), a well-marked "Linnean" species 

 where there are so few individuals — perhaps a dozen in this case 

 — that they do not allow of a great range of variation. There is 

 also less range in the small "Jordanian" species, but these, on 

 the theory of differentiation, are later phases in evolution than 

 are the Linnean species. As one of the latter increases in number, 

 and in occupied area, from its first beginning, and thus probably 

 comes into greater variety of conditions, and into more crossing 

 with other individuals, the more variation does it show, on the 

 whole (p. 159). 



The following quotation shows the point of view that is being 

 taken up as the result of the work of agricultural geneticists; 

 *' Studies of crop populations have shown that natural selection 

 does not result in the survival of the fittest type, but of the fittest 

 'population, and the fittest population is almost always a mixture 

 of many types" (78). This agrees with the ordinary observation 

 of everyday life, that natural selection is individual in its action. 



The plants (or group, occupying the whole of the locality) that 

 did not show the useful improvement (or another as good) were 

 killed out in the struggle for existence, that also killed out the 

 parent, which was assumed not to become adapted. 



It is clear that there are many weak points in the Darwinian 

 position, and to support them all kinds of assumptions and sup- 

 plementary hypotheses have been brought up. But there has 

 never been any good proof (1) that evolution proceeded essen- 

 tially by improvement in adaptation, (2) that it was gradual and 

 closely continuous, (3) that the phenomena of the structure of 

 plants reflect the adaptation that has gone on in them, or (4) that 

 groups of plants can compete as units. 



When one comes to look into the matter, one soon realises that 

 the theory of natural selection rests upon a great many assump- 

 tions, sometimes backed by more or less proof, sometimes not. 



