PAPERS PRESENTED AT GENERAL SESSIONS 31 



out of court. Now, however, we have discovered that 

 the inheritance of acquired characters is possible in 

 many organisms under certain conditions, especially in 

 the simpler organisms. This means that Lamarckism is 

 coming into notice again, and there is a decided revival 

 of interest in a modern modified form of this explanation. 



A single simple illustration of the work on the inherit- 

 ance of acquired characters in plants may he given. 

 A great many plants have been used in experimental 

 work of this kind. In investigating the periodicity of 

 sexual cells in Dictyota, a marine alga, Williams has 

 proved the possible inheritance of acquired characters. 

 In a given locality the male and female organs develop 

 simultaneously, and a general liberation of gametes and 

 fertilization take place on a particular day. This date 

 differs in different localities, showing a relation to tides 

 and therefore to the amount of available light. On the 

 other hand, there is no evidence of periodicity in seas 

 where there are no tides. Plants transferred to the lab- 

 oratory, and thus removed from tides and varying light, 

 continue to show the characteristic periodicity of the 

 locality from which they came. Here is an obvious 

 adjustment of the plant to a varying set of environ- 

 mental conditions which has become hereditary. 



As perhaps many of you know, very recently much 

 more important and convincing testimony as to the 

 inheritance of acquired characters has been secured by 

 Guyer in his experimental work on eye defects in white 

 rabbits. In short, there seems to be no doubt but that 

 acquired characters may be inherited. 



Darwin's explanation encountered the obstacle of 

 variations of a sort that were claimed to be inadequate 

 to account for the results of evolution. It ought to be 

 kept in mind that this objection does not involve the idea 

 of natural selection. That such selection occurs is ob- 

 vious, for some forms survive and others perish, but 

 does this result in building up new species with these 

 small variations we call continuous ? The question 

 whether Darwin's variations are adequate for his con- 

 clusion is being examined critically by geneticists. 



