308 THE EVOLUTION THEORY 



to a greater or less degree. And these variations may be in a quite defi- 

 nite direction, persisted in for internal reasons, as we have already seen 

 in the section dealing with germinal selection. These variations are the 

 building-stones out of which, under the guidance of personal selection, 

 a new specific type, that is, a new complex of adaptations, can be 

 established. In this type many indifferent characters are involved, 

 which are just as constant characters of the species as the adaptations. 

 The opponents of the selection theory have often urged against 

 it this constancy of indiftei'ent characters, but as soon as we cease 

 to restrict the principle of selection to ' persons,' and extend it also 

 to the lower categories of vital units, the occurrence of indifferent 

 characters is easily understood. To illustrate characters of this kind, 

 Henslow has recently called attention to the species of gentian, whose 

 flowers have a corona split into five tips in some species and into six 

 or seven in others, and we cannot possibly ascribe any biological 

 significance to these specific characters. It is quite possible that they 

 possess none ; but did not even Darwin express his belief that many 

 peculiarities of form ' are to be attributed to the laws of growth, and 

 to the mutual influence of parts,' forces which he rightlj' refrained 

 from including under ' natural selection ' in his sense of the word, but 

 which we now regard as an expression of intra-selection or of histonal 

 selection? It is this, in our opinion, which brings about the coadapta- 

 tion of the parts to form a harmonious whole, which admits of the 

 primary adaptations to the conditions of life being followed or accom- 

 panied by correlative secondary variations, and which plays an 

 important part in directing the course of every individual develop- 

 ment, and is therefore uninterruptedly active within the organism. 

 We cannot analyse the factors precisely enough to be able to demon- 

 strate in an individual case why the corona should be divided into 

 four in one species of gentian and into fi^■e in another, but we can 

 understand in principle that all adaptations of a species which are not 

 primary are determined by the compelling influence of intra-selection. 

 And we need not now rest content even with that, for we know that 

 this intra-selection — as we have already seen — is active within the 

 germ-plasm, and it is only a logical consequence of the principle of 

 germinal selection to suppose that variations of definite determinants 

 due to personal selection may in the germ-plasm itself give rise to 

 correlative variations in determinants next to them or related to 

 them in any way, and that these may possess the same stability as 

 the primary variation. This seems to me a sufficient reason why 

 biologically unimportant characters may become constant characters 

 of the species. Correlation is not effected only in the perfect 



