ORIGIN OF THE SPECIFIC TYPE 343 



species, and, moreover, so far no one has succeeded in rearing these 

 artificial lichens for any length of time, still less in seeing them 

 evolve into specific forms persistent in natural conditions. 



But if this supposition should prove to be not only improbable, 

 but actually erroneous, then the existence of Lichens would afford 

 a clear proof that the ' type ' of the species does not depend essentially 

 upon the constant intermingling of individuals, but upon a process 

 which we may best designate uniforonity of adaptation. We have 

 simply to suppose that under similar externa] influences similar 

 variational tendencies were started by germinal selection in all the 

 individuals of the two parent species of a lichen, and set a-going 

 by germinal selection, just as a warmer climate gives rise to a black 

 vai'iety in the butterfly Folyommatus 2M<xas, because similar deter- 

 minants of the germ-plasm of all the individuals were impelled to 

 vary in the same manner and direction. This would then give rise 

 to quite definite variations, and since only the suitable variational 

 tendencies could survive, primitive though never complicated adapta- 

 tions would arise. But we cannot assume that the lichens are not 

 adapted to the conditions of their life as well as all other organisms. 

 We cannot judge how far even their shape is to be regarded as an 

 adaptation, whether the formation of encrusting growths, of tree-like 

 forms, of cup or bush-lichens, may not be regarded as adaptations 

 towards a full utilization of the conditions of their life — but even 

 if this is not the case, the formation of soredia remains an undoubted 

 adaptation to the symbiosis of those lichens which exhibit them. 

 The soredia cannot depend upon the direct effect of the conditions 

 of life, for they are reproductive bodies which did not exist before 

 the existence of the lichen, and only originated to facilitate their 

 distribution. 



Thus there is still a great deal that is doubtful in our theories as 

 to the transformations of organisms, and much remains still to be 

 done. But even though we may doubt whether adaptations could 

 come about in multicellular organisms without amphigony, we may 

 be quite certain of the converse, that is, that the specific type can 

 be changed in every individual feature by natural selection on 

 the basis of amphigony, even as regards invisible features which only 

 express themselves in altered periods of growth. Even when there 

 is no isolation whatever and no mutual sterility, and when a mobile 

 species is uniformly distributed over a large area, a splitting up into 

 races in regard to one particular character may occur, simply through 

 adaptation to the spatially different climatic conditions of the area 

 inhabited. 



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