DISTRIBUTION OF ANIMAL COMMUNITIES 7 



than it really is, and that it should not be possible to say that 

 " ecology consists in saying what every one knows in language 

 that nobody can understand." The writer has learnt a far 

 greater number of interesting and invaluable ecological facts 

 about the social organisation of animals from gamekeepers 

 and private naturalists, and from the writings of men like 

 W. H. Hudson, than from trained zoologists. There is some- 

 thing to be said for the view of an anonymous writer in Nature, 

 who wrote : " The notion that the truth can be sought in 

 books is still widely prevalent and the present dearth of 

 illiterate men constitutes a serious menace to the advancement 

 of knowledge." Even if this is so, it is at the same time true 

 that there is more ecology in the Old Testament or the plays 

 of Shakespeare than in most of the zoological textbooks ever 

 published ! 



All this being so, there seems to be no point in making 

 elaborate and academic classifications of animal communities. 

 After all, what is to be said for a scientist who calls the 

 community of animals living in ponds the '' tiphic asso- 

 ciation," or refers to the art of gardening as " chronic 

 hemerecology " ? 



3. It is important, however, to get some general idea of the 

 variety and distribution of the different animal communities 

 found in the world. The existence of such a rich variety of 

 communities is to be attributed to two factors. In the first 

 place, no one animal is sufficiently elastic in its organisation 

 to withstand the wide range of environmental conditions 

 which exist in the world, and secondly, nearly all animals tend 

 during the course of evolution to become more or less specialised 

 for life in a narrow range of environmental conditions, for by 

 being so specialised they can be more efficient. This tendency 

 towards specialisation is abundantly shown throughout the 

 fossil record and is reflected in the numerous and varied 

 animal communities of the present day. Primarily, there is 

 specialisation to meet particular climatic and other physical 

 and chemical factors, and secondarily, animals become adapted 

 to a special set of biotic conditions — food, enemies, etc. The 

 effect of the various environmental factors upon animals is a 



