336 THE POPULAR SCIENCE MONTHLY 



organic rank, but also because most of the varying environments within 

 any one civilization are not absolutely imposed upon the individual, 

 as are experiments upon the lower organisms. This is not meant to 

 imply that differences between one historical age and another, or any 

 other imposed environment from which there is no escape, may not 

 be found of considerable importance in relation to certain sociological 

 and historical facts. For instance, the total number of eminent men in 

 western Europe probably increases too rapidly from the fourteenth cen- 

 tury to the sixteenth not to be in part due to the force of circumstances. 49 

 Also I have statistics in the course of compilation which indicate that 

 there is evidence that women are advancing in noteworthiness of 

 achievement in the United States with each elapsed decade. These 

 imposed and unescapable conditions, which change with the course 

 of history and affect entire races or great groups of people, must be 

 clearly distinguished from the class of environments that exist within 

 any one age and in any one state of civilization. 



There are doubtless other ways in which man and other mammals are 

 directly modified by their environment in an essential and lasting way, 

 but to enter into a discussion of these questions is useless in connection 

 with this generalization. Such are the modifications produced by 

 poisons, diseases of a bacterial or other nature, which the individual 

 accidentally encounters. The necessaiy knowledge has not yet been 

 gained for any generalization, from a comparative point of view, in re- 

 gard to these complicated processes, so that we should be able to say 

 that these changed conditions affect higher organisms more than lower 

 Moreover, the same poison may be for one kind of protoplasm a great 

 change and for anotber a slight one, and we have already seen that the 

 proportionate amount of change in the outward conditions is necessarily 

 of prime importance in determining the end result. 



These chemical questions do not fall within the literature contained 

 in text-books of experimental zoology, which, to review and rearrange 

 has been the chief purpose of this article. The entire analogy of such 

 experiments, as well as the results of special studies on the relative 

 influence of heredity and environment, can lead to but one conclusion, 

 and that is, that the value of modification diminishes as evolution 

 proceeds. 



I know that to generalize is dangerous and exceptions may be 

 found which seem to conflict with the laws or principles which are 

 here set forth, but often apparent exceptions find explanation in the 

 light of further knowledge. I put these laws forth with some hesitancy, 

 yet feel that enough is known to take a step beyond hypotheses and 

 trust that the future will confirm their essential truth. 



49 This would be the conclusion from Cattell's " Statistical Study of Emi- 

 nent Men," Popular Science, February, 1903, and Ellis's " Study of British 

 Genius," p. 12. 



