32 ANIMAL ECOLOGY 



understand plant communities, and therefore animal com- 

 munities, much more easily than he can otherwise do, by 

 providing an idea which links up a number of otherwise rather 

 isolated facts. Furthermore, as will be shown later on, suc- 

 cession of communities, which is nothing more than a migration 

 of the animals' environment, plays an important part in the 

 slow dispersal of animals. Again, as we have pointed out, 

 the intricate problems of competition between different species 

 of animals can be studied to advantage in a series of changing 

 communities. Tansley's Types of British Vegetation i^ is the 

 standard work in which the plant associations of Britain are 

 described, and in many cases the probable lines of succession 

 in the associations are given also. It is essential to have access 

 to this book if one is carrying out any extensive work in the way 

 of preliminary surveys or studies in ecological succession. 



