430 The American Naturalist. [May, 
after an enormous interval of time does actual elimination 
occur, Abnormal nervous conditions such as seen in Anen- 
cephaly are accompanied by the revival of a large number of 
latent characters. In Galton’s language, patent characters be- 
come latent in the course of evolution. 
In Weismann’s language, on the other hand, in explanation 
of dimorphism in hymenoptera and other types, there are cer- 
tain sets of biophors corresponding to certain possibilities of 
adult development. Apply this to the celebrated case of the 
flat-fishes and the remarkable results recently obtained by 
Agassiz, Filhol, and Giard in artifically producing more or less 
symmetrical flat-fishes by retaining the young near the surface. 
Weismann’s interpretation of the evolution of flat-fishes has 
always been that it was by the selection of asymmetrical and 
elimination of symmetrical ‘determinants.’ In the light of 
these experiments he must now recast this explanation by say- 
ing that the flat-fishes have kept in reserve a set of symmetrical 
‘determinants’ since the period when our first record of the 
asymmetrical type appears, or about three million years! 
This attack upon the speculations of one writer is a digres- 
sion. What I really wish to bring out is the necessity of a 
far more critical analysis of the various kinds of evidence for 
Buffon’s factor. This necessity may be illustrated by the 
different interpretations of color change in direct response to 
changed environment. 
The most significant experiments upon color are those of 
Cunningham upon the flat-fishes. He has proved that during 
the early metamorphosis of young flat-fishes, when pigment is 
still present on both sides, the action of reflected light does 
not prevent the disappearance of this pigment upon the side 
which is turned towards the bottom, so that the color passes 
rapidly through a retrograde development; but prolonged 
exposure to the light upon the lower side causes the pigment 
to reappear, and upon its reappearance the pigment spots are in 
all respects similar to those normally present upon the upper 
side of the fish. It is very important not to confuse these 
results, of deep interest as they are, with those obtained where 
the environment is new in the historic experiefice of the organ- 
