74 ADAPTATION AND PROGRESS 
unknown nature, that may, in the last analysis, be psychical in 
nature.” 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.” ? 
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 [bid., p. 120. 
