The Theory of Evolution 231 



as we have supposed, external conditions may sometimes cause 

 adaptive changes in adult organisms, i.e. in their body-cells, 

 and if the egg is at times similarly affected so that the next genera- 

 tion shows from birth the same changes; and further if these 

 general changes are mutations, i.e. fixed in character, it will 

 appear as though the process of adaptation and of evolution has 

 taken place at the same time. It appears, however, when the 

 whole field of variation is examined that this is only a special 

 case. In other cases the changes affected by external conditions 

 may be different from those brought about in the germ-cells, 

 and some of the new mutations may be adapted to a different 

 environment, or to the old one in a different way. In both cases 

 the problem is fundamentally the same, and it is the process of 

 variation that is our real problem. 



Lloyd Morgan, Osborn, and Baldwin have suggested that adult 

 animals may at times become adapted to a new environment 

 by a direct response, as by the use and disuse of certain organs 

 of the body, and maintain themselves in this way until the proper 

 germinal variations occur that fix, as it were, the new characters 

 so that they become a part of the permanent inheritance of the 

 species. Thus the organism, owing to its power of responsive 

 adaptation, adjusts itself to a suitable environment and awaits 

 the- time when the fixation of the new characters may success- 

 fully be accomplished as the result of a germinal variation of 

 the right sort. It is assumed that fluctuating variations bring 

 about the permanent change, but obviously a mutation would 

 give the same result. To what extent the advent of the new 

 variation, whatever its origin, is anticipated in the way assumed, 

 is not known. On the mutation theory it is doubtful whether 

 this subsidiary assumption is needed to explain how new species 

 arise. On the theory of the selection of fluctuating variations 

 the assumption of "organic adaptation" seems to cover an ad- 

 mitted weakness of Darwin's theory, but whether the selection of 

 fluctuating variations could ever fix permanently a character is 

 a question that seems from the experimental evidence to be 

 answered in the negative. 



