PHYSIOLOGY AND ECOLOGY 35 



same species (man). He suggests that the social psychology of man 

 may be traced to the inter-psychology and physiology of the lower 

 animals. If this is true, then we can be more certain that the inter- 

 psychology of the higher forms has developed from the inter-physiology 

 of the lower forms (55 and citations). To this should be added the 

 behavior between different species, while acting or living together as 

 one. In the steppes ecologically similar animals frequently act as one 

 species. Mr. Roosevelt has said that one of the most interesting features 

 of African wild life is a close association and companionship often seen 

 between totally different species of game (3). Mr. Roosevelt shows 

 the zebra and hartebeest herding together, (b) Inter-mores physiology 

 (between ecologically dissimilar forms, or antagonistic forms). — The 

 relations of animals of different size, habits, etc., to one another involve 

 some of the most striking features of behavior. Much of the behavior 

 which tends to protect animals from enemies falls under this head. 1 



In all cases of modification of behavior by the physical environment 

 or by relations to other animals of the community and in all cases where 

 the habitat is selected, the habitat is the mold into which the organism 

 fits. The study and analysis of the habitat is a necessity as soon as the 

 selection of habitat and the adjustment of behavior and physiological makeup 

 to the environment are shown to be general facts. Since habitats are differ- 

 ent, animal communities occupying different habitats are physiologically 

 different for the reasons just given. 



The relations of the animals which make up communities are 

 relations of life histories. The life histories of the different species are so 

 adjusted to conditions that all animals do not reach maturity and greatest 

 abundance at the same time. Some species continue throughout the 

 season; for example, mammals because of their long lives, and some 

 species of aphids or copepods because of their great fecundity and 

 peculiar physiological makeup. There is a succession of mature or 

 breeding animals with the change of season. A similar phenomenon 

 is noticeable in plants. Such succession is called seasonal succession 

 (47, 56). Different species of the same community come into relation 

 at different seasons of the year. 



Communities are systems of correlated working parts. Changes are 

 going on all the time as a sort of rhythm much like the rhythm of activity 

 in our own bodies related to day and night. In addition to this, com- 

 munities grow by the addition of more species, decline, and finally 



1 It is at this point that ecology comes into contact with the theories of natural 

 selection, adaptation, mimicry, etc. 



