74 ADAPTATION AND PROGRESS 



unknown nature, that may, in the last analysis, be psychical in 

 nature." 1 Though not a neo-Lamarckian, Professor Wilson 

 makes room for environmental influences to affect the germ 

 plasm and so influence heredity. " Though we may not fully 

 understand the manner in which the germ cells are modified, 

 there is no inherent improbability or difficulty in the conception 

 that such modifications will produce blastogenic variations or 

 mutations that are inherited, permanently or temporarily. We 

 can readily understand that the constitutional effects of tempera- 

 ture, food, moisture, and similar general agencies of the environ- 

 ment may manifest themselves in definite changes that reappear 

 in following generations because the germ cells have been directly 

 affected in the same way as the somatic cells." 



D. T. MacDougal of the Carnegie Institution of Washington 

 took a position very like that of Wilson, holding that " the 

 securest foundation is laid for the conclusion that well-defined 

 correlations exist in the plant by which secondary effects of the 

 action of external factors, or of morphogenic or embryonic 

 procedure, may be freely communicated from one part of the 

 soma to another and from the egg to the soma." 2 



Charles B. Davenport also of the Carnegie Institution and 

 Secretary of the American Genetic Association championed the 

 cause of mutation, and Professor Eigenmann advocated " selec- 

 tive adaptations " as a factor to be reckoned with. " Adapta- 

 tions," he says, " have usually been looked upon as adjustments 

 in the organism to its environment. The suggestion has more 

 recently been made that adapted environments and habits are 

 selected by animals adjusted to them. . . . The shore-fishes, 

 channel-fishes, etc., depending on light to find their food and 

 mates, moved out to the Green River, where their descendents 

 live to the present day. The fishes negatively heliotropic, 

 nocturnal, or stereotropic, moved into the holes dissolved in the 

 bottom of the river, followed its subterranean development, and 

 their descendents live today in the stream which now flows 

 entirely below the valley. . . . Primarily blind fishes do not 

 have degenerate eyes because they live in caves, but they live in 



1 Fifty Years of Darwinism, p. 109. 2 Ibid., p. 120. 



