34 Outline of Genetics 



removed from the influence of tides and varying light, 

 continued to show the characteristic periodicity of the 

 locaHty from which they came. Thus an obvious adjust- 

 ment on the part of the plant to a varying set of environ- 

 mental conditions has evidently become heredity. 



It would be unwise to attempt any final conclusions 

 on this subject of inheritance of acquired characters; 

 the status of the subject changes as new evidence is 

 gathered. Such evidence as we have considered, how- 

 ever, recommends the following tentative conclusion. 

 Inheritance of acquired characters is possible in many 

 organisms. This possibility is more often realized per- 

 haps in the simpler than in the more complex organisms. 

 In the latter, an unusual set of conditions is required, 

 such that the well-insulated germ plasm will be reached. 



From the point of view of the geneticist, the small 

 amount of inheritance of acquired characters that might 

 take place is usually negligible. The geneticist deals 

 almost entirely with characters the origin of which is 

 either entirely unknown or 'Spontaneous" (mutation) 

 and not clearly traceable to any specific environmental 

 conditions. For the evolutionist, however, this phenom- 

 enon becomes very significant. The recent appearance 

 of seemingly irrefutable instances of inheritance of 

 acquired characters, taken together with the growing 

 conviction that mutation does not provide the type of 

 change necessary to account for progressive evolution 

 (see chapter on ' 'Mutation"), is leading to a revival, in 

 modified form, of the Lamarckian view. 



