32 COMMUNITY FUNCTIONS— DYNAMICS OF BIOTIC FORMATION 



Such adjustments are often correlated with more or less striking adap- 

 tations, clearly so with most plants, but less evident and frequent 

 with animals. When adjustment has once been stabilized as a special 

 adaptation, a certain degree of plasticity or power of reversion is lost, 

 and new adjustments and adaptations follow a different course. A 

 somewhat similar result occurs when correlation or competition be- 

 tween organs or parts enters to produce effects not directly correlated 

 with the habitat and hence apparently opposed to the rule. 



The viewpoint as regards structural adaptations in sessile animals 

 is similar to the older views held regarding land plants (Wood-Jones, 

 1910). W'ith land plants, the causal sequence that terminates in adap- 

 tation may operate upon the individual, the species, or the commu- 

 nity. Actually, it affects the individual directly and concretely, and 

 the phyletic and social groups in conseciuence. In respect to the 

 species-individual or specient, these effects are summed up by the life 

 history in terms of adjustment, and in the life form, etc., in so far 

 as they deal with adaptation. With respect to the community, ad- 

 justment is represented by a series of basic processes or functions, and 

 adaptation by the structures expressed in the climax and serai com- 

 munities of different rank. It is obvious, however, that in a dynamic 

 system life history and life form are constantly interdependent, and 

 that the modification of either organism or community carries in- 

 escapable consequences to the other (Clements, 1931). 



In motile animals, structural adaptations are preeminently related 

 to activity. From the standpoint of community relation, the signifi- 

 cant activities are connected with layers or strata of the community, 

 and hence adaptation is to epiphytic life, especially arboreal in the 

 larger species, to cursorial and to subterranean life. Such modifica- 

 tions are noteworthy, but they may bear no definite relation to the 

 community as a whole: for example, subterranean adaptations in the 

 tundra are hardly distinguishable from those of the tropical grass- 

 land. However, the fact of their existence may be an element of 

 much importance in both communities through the activities corre- 

 lated with them. 



Animal organisms come into existence with certain innate behavior 

 characteristics. Some of these are simple reflexes, such as backing off 

 and turning in Paramecium; others are complicated activities. In the 

 larger and more influent animals, these innate or instinctive characters 

 are the basis of the selection of food and habitation and the formation 

 of habits, and thus determine the course of reaction and coaction 

 phenomena. Associative memory and intelligence play an important 

 part in the activities, coactions, and reactions of the vertebrates, 



