OECOLOGICAL FEATURES OF EVOLUTION. 
BY E. C. CASE. 
The attention that has been called to the principle of adaptive 
radiation by the recent papers of Prof. Osborn and his followers 
in the American Naturalist has led to the suggestion that some 
good might be derived from viewing the subject from a slightly 
different standpoint. Osborn has concerned himself with a 
demonstration of the fact that in successive periods the various 
phyla have developed in a diffuse way producing a large number 
of forms peculiarly adapted to the local conditions and that this 
process has been repeated with close similarity in each period. 
Other writers have concerned themselves with the way in which 
the adaptations have been produced; all writers have looked at 
the subject from the standpoint of the animal. ' It seems worth 
while to look at the subject from the standpoint of the environ- 
ment ; to analyze the environment in order to detect its possibili- 
ties in influencing the change in the animal form. 
For the purposes of the discussion it is recognized that adap- 
tation is as much a fact as heredity and its processes as much of 
a mystery. With the processes the dicussion has nothing to do 
nor even whether the environment induces the adaptations ; it is 
assumed that the environment changes and that the adaptation 
follows the environment. 
Most of the points gone over have been discussed before and 
are even the classics of the literature of evolution but so far as I 
know no one has attempted to place the environment in the fore- 
ground of the discussion. This our increasing knowledge of the 
principles of physiography and of the climate and surface of geo- 
logical areas will enable us to do with increasing value. 
New names do not explain old problems and the few intro- 
duced here are only used for the purposes of clarity. 
For simplicity in approaching the subject let us take a con- 
crete example. An animal (the principles seem equally applica- 
ble to plants but the author's limitations compel him to turn to 
animals for illustrations) £>f generalized structure and potential 
variability enters by migration a new region ; the overwhelming 
chances are that it will encounter one of two conditions, either 
the sum of its contacts with its new environment (using the term 
environment in its widest sense, food, competion, enemies, 
climate, surface, breeding places, etc.,) will be hostile to the new 
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