CHAPTER II. 



THE ELEMENTARY FACTS OF DISTRIBUTION. 



Importance of Locality as an essential character of Species — Areas of Dis- 

 tribution — Extent and Limitations of Specific Areas — Specific range of 

 Birds — Generic Areas — Separate and overlapping areas — The species of 

 Tits as illustrating Areas of Distribution — The distribution of the species 

 of Jays — Discontinuous generic areas — Peculiarities of generic and 

 family distribution — General features of overlapping and discontinuous 

 areas — Restricted areas of Families — The distribution of Orders. 



So long as it was believed tliat the several species of animals 

 and plants were " special creations," and had been formed 

 expressly to inhabit the countries in which they are now found, 

 their habitat was an ultimate fact which required no explana- 

 tion. It was assumed that every animal was exactly adapted 

 to the climate and surroundings amid which it lived, and that 

 the only, or, at all events, the chief reason why it did not 

 inhabit another country was, that the climate or general con- 

 ditions of that country were not suitable to it, but in what 

 the unsuitability consisted we could rarely hope to discover. 

 Hence the exact locality of any species w^as not thought of 

 much importance from a scientific point of view, and the idea 

 that anything could be learnt by a comparative study of 

 different floras and faunas never entered the minds of the 

 older naturalists. 



But so soon as the theory of evolution came to be generally 

 adopted, and it was seen that each animal could only have 

 come into existence in some area where ancestral forms closely 

 allied to it alrea^dy lived, a real and important relation was 



