ANIMALS AND THEIR ENVIRONMENTS ADAMS. 



539 



Table 2. — The genesis and formation of inland habitats in a humid climate and 

 the dynamic status of the processes. 



Dynamic status. 



Phases in the formation of inland environments. 



I. Unstable equilibrium — condition 

 of stress or pressure. 



Original conditions; elevated land area, or new land surface, or 

 begimiing of new cycle. 



II. Process of adjustment to stress 

 or strain. 



Process of formation of habitats; all habits are constructive. 



Derived conditions; lowland area, old land surface (base-leveled 

 to the marine environment), end of a cycle, or dominance; 

 under relatively stable conditions. 



The preceding discussion is based upon the conditions of a humid 

 climate, but the semiarid and the arid climates should also be touched 

 on. In time, as ecological studies are extended to all kinds of land 

 areas, it will be possible to formulate all of the general principles of 

 the origin or process of development of land habitats ; but at present 

 vast areas of the land have never been observed by a zoologist from a 

 modern ecological standpoint. Most of the ecological studies of ani- 

 mals have been carried on in a humid climate, only slight attention 

 having been given to the ecological relations existing in an arid cli- 

 mate, and still less to those in alpine and polar regions. After the 



