226 THE PROBLEMS OF EVOLUTION 



play a part in successful experimentation. For 

 this reason a second stage of investigation should 

 be undertaken to relate the artificially developed 

 character with some condition of the external 

 environment as an adaptive character. It is more 

 than likely that the attainment of this end will 

 be diflBcult, but it is essential to a thorough study 

 of the problem. 



With a character developed artificially by modi- 

 fication of the environment through several genera- 

 tions, and an adaptive association established be- 

 tween it and some other environmental condition, 

 the possibility arises of new development through 

 use, in the ordinary sense of the word, of the pre- 

 viously indifferent character. The essential condi- 

 tion to be investigated, however, is the potency of 

 the adaptive value of the character to maintain it 

 even in the absence of the environmental condi- 

 tion under which it originally developed. Mainte- 

 nance of the adaptive association in an artificial 

 environment and the abatement, at the same time, 

 of the original stimulus, would determine this point. 



These are the conditions necessary for an accept- 

 able and final investigation of the inheritance of 

 acquired characters. Whether they can be com- 

 pletely attained remains to be determined. It is 

 certain that the attainment will be difficult, for 

 the available organisms have had many years in 

 which to adjust themselves to the natural environ- 



