ECOLOGY 273 



of the leaf-stalks. These serve as dwellings, and glands near the tips of the 

 leaves furnish food. The ants which inhabit acacias are very pugnacious 

 and have very potent stings. They drive away leaf-cutter ants and other 

 enemies. The cecropias provide many small chambers for dwellings within 

 their stems. They also supply food along their leaf stalks, but many of their 

 ants procure their food largely from plant lice which are kept in the cham- 

 bers inside the stems. The ant plants in Asia are usually somewhat sponge- 

 like, with intercommunicating spaces within a fleshy body and many 

 small openings on the exterior. In British Guiana, Wheeler studied an ant 

 plant which had about fifty species of animals associated with it. These 

 included twenty-eight species of ants, besides beetles, crustaceans and 

 other things. 



The various associations between plants and animals not only show the 

 interdependence between the two, but also add to the evidence concern- 

 ing the high degree of adaptation that all animals show to the particular 

 environments in which they live. Animals are just as strikingly adapted to 

 the living things which surround them as to the non-living. 



>>><<<■ 



SOME ADAPTATIONS TO THE ENVIRONMENT * 

 HORATIO HACKETT NEWMAN 



"The adaptation of every species of animal and plant to its environ- 

 ment," 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. 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." 



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. 



If the organism fits the environment, no less certainly must the environ- 

 ment fit the organism. Professor Lawrence J. Henderson points out that 

 the environment, no less than organisms, has had an evolution. There is 

 hardly an element of the effective environment that could be changed 

 without causing the extinction of life or at least the transformation of it 

 so profound that it might not be hfe at all as we know life. Water, for ex- 



* Reprinted from Evolution, Genetics, and Eugenics by Horatio Hackett Newman 

 by permission of the University of Chicago Press. Copyright 1925. 



