734 TEXTBOOK OF ZOOLOGY 



or the species. Similarly the sum total of physical environment as 

 expressed in climate has been stressed rather than single factors, 

 such as moisture, temperature, light, etc. The animal in nature is 

 subject always to the action of a complex environment and its dis- 

 tribution and reactions are the result of its response to the whole. 

 The student is referred to the chapter on Animal Behavior for a 

 discussion of the response of the individual organism to modifica- 

 tions in single environmental factors. 



