CHAPTER XIV 
THE BACKGROUND OF DARWINISM 
ADAPTATIONS 
H. H. NeEwMAan 
“The adaptation of every species of animal and plant to its 
environment,” says Jordan and Kellogg,’ “is a matter of everyday 
observation. So perfect is this adaptation in its details that its main 
facts tend to escape our notice. The animal is fitted to the air it 
breathes, the water it drinks, the food it finds, the climate it endures, 
the region which it inhabits. All its organs are fitted to its functions: 
all its functions to its environment. Organs and functions are alike 
spoken of in a half-figurative way as concessions to environment. And 
all structures and powers are in this sense concessions, in another 
sense, adaptations. As the loaf is fitted to the pan, or the river to its 
bed, so is each species fitted to its surroundings. If it were not so 
fitted, it would not live. But such fitness on the vital side leaves large 
room for variety in characters not essential to the life of the animal.” 
The authors quoted above appreciate what is perhaps the most 
significant fact about adaptations: that the adaptations are to a large 
extent molded by the environment and therefore fit the environment. 
So long as the environment remains uniform, a given species will 
remain unchanged, except for minor fluctuations and occasional 
mutations; but if the environment changes, sometimes even slightly, 
the development of the individual responds in such a way as to give a 
radically different end product. So we may conclude that a large part 
of the fitness of the organism to the environment is due to the fact that 
the development of each individual is molded by the environment so as 
to fitit. Thus some at least of the apparent mystery of adaptations is 
dispelled. 
When we think of the fitness of the organism to the environment 
we take an entirely one-sided view of the matter, for if the organism 
fits the environment, no less certainly must the environment fit the 
organism. ‘This idea of the “fitness of the environment” has been 
* From D. S. Jordan and V. L. Kellogg, Evolution and Animal Life. 
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