520 SOCIAL ASPECTS OF BIOLOGICAL RESULTS 



new conditions of stimulus, both positive and negative, is 

 obvious. Now, the important point is that we cannot with 

 any certainty count these "modifications" as part of the raw 

 material of evolution (progressive or retrogressive), for we have 

 no good evidence to show that they can be hereditarily entailed 

 as such, or even in any representative degree transmitted to 

 the offspring. 



It is admitted that some deeply-saturating modifications 

 may, by affecting the nutritive stream, indirectly affect the 

 germ-plasm, but there is no proof of the transmission of any 

 modification as such. The evidence for this assertion will be 

 found, foi' instance, in preceding chapters. 



It is admitted that the organism — notably the human or- 

 ganism — is often extraordinarily modifiable, and that similar 

 conditions may induce similar modifications on generation 

 after generation, so that an appearance of heritability results. 



Moreover, as Professors Mark Baldwin, Lloyd Morgan, and 

 H. F. Osborn have pointed out, modifications that are effectively 

 advantageous — adaptive responses, in fact — may have an in- 

 direct evolutionary importance, for they may serve as sheltering, 

 life-preserving, or welfare-furthering screens until coincident 

 endogenous variations in the same direction have time and 

 opportunity to establish themselves. Thus a modificational 

 change may be gradually replaced by a strictly variational, and, 

 by hypothesis, heritable one. Then the screen or veneer may be 

 done without. 



If the conclusion of the majority of biologists be correct, 

 that modifications are not as such transmitted, there are some 

 obvious sociological corollaries. We have, in the progress of 

 education, therapeutics, and hygiene, unceasingly striking 

 evidence that the human organism is very plastic ; but we 

 cannot delude ourselves with the belief that its precise gains 

 or losses are ever as such transmitted. Therefore, it has to be 

 our practical endeavour that advantageous modifications be 



