DISTRIBUTIO'N^ OF SPECIES 13 



in the word species, but that he may take it as meaning the 

 same as kind, in regard to animals and plants in a state of 

 nature, and that he will have no difficulty in following the 

 various discussions and expositions in which this term is nec- 

 essarily so prominent. The reason why species is the better 

 term is because hind is used in two distinct senses — that of 

 species when we speak of kinds of deer, of squirrels, or of 

 thrushes, but also that of a genus or a family when we 

 speak of the deer, squirrel, or thrush kind, as meaning the 

 whole group of these animals. If we used the word tribe 

 instead of hind in this latter sense, all ambiguity would be 

 avoided. 



Eew persons who have not studied some branch of natural 

 history have any idea of the vast extent, the infinite variety, 

 the omnipresence and the intermingling of the varied species 

 of animals and plants, and still less of their wonderful co-adap- 

 tation and interdependence. It is these very characteristics 

 that are least dwelt upon in books on natural history, and they 

 are largely overlooked even in works on evolution. Yet they 

 form the very basis of the phenomena to be explained, and 

 furnish examples of development through survival of the fittest, 

 on a larger scale and often of easier comprehension than the 

 special cases most frequently adduced. It is this ground-work 

 of the whole subject that we will now proceed to consider. 



The Distribution of Local and ^yorld Species 



The first important group of facts which we have to con- 

 sider is that which relates to the number of existing species 

 of the tw^o great divisions of life, plants and animals, and their 

 mode of distribution over the earth's surface. 



Every one who begins to study and collect any gToup of 

 animals or plants is at once struck by the fact that certain 

 fields, or woods, or hills are inhabited by species which he can 

 find nowhere else ; and further, that, whereas some kinds are 

 very common and are to be found almost everywliere, others 

 are scarce and only occur in small numbers even in the places 



