390 ADAPTIVE VARIATIONS. 



great importance in the evolution of more adaptive 

 forms; in some cases, perhaps, of greater importance 

 than genetic variations. Supposing, for instance, a 

 number of organisms are more or less suddenly exposed 

 to a considerable change of environment, whereby the 

 majority of them are killed off. The survivors will be 

 those which had the greatest power of adaptation to 

 the new surroundings, and though the somatic varia- 

 tions will not be, as such, inherited, yet the survivors 

 will be, on the whole, those organisms which originally 

 possessed the largest proportion of the particular char- 

 acters which have appeared as adaptive somatic varia- 

 tions. That is to say, adaptive somatic variations are, 

 on an average, a magnified image of similar, but much 

 more minute genetic variations, and hence the average 

 hereditary characters of the survivors are in the direc- 

 tion of adaptation. Again, the survivors will be those 

 individuals possessing the largest degree of innate 

 adaptability to the particular environment in question. 

 Hence their offspring will also possess this adaptability, 

 and in that they will have been exposed to the changed 

 environment throughout the whole period of develop- 

 ment, they will show much more marked somatic varia- 

 tions than those shown by their parents. Finally, if it 

 be admitted that the effects of conditions of life may 

 be in some degree cumulative, then the adaptation of 

 the second generation to the environment will be from 

 this cause still further increased. Views somewhat 

 similar to these as to the importance of somatic varia- 

 tions have been set forth, at considerable length and 

 with admirable lucidity, by Professor Lloyd Morgan in 

 his work on " Habit and Instinct " (p. 316), and to this 



