CHAPTER II 



SPECIES THEIR NUMBERS, VARIETY, AND DISTRIBUTION 



WHEN we begin to inquire into the main features, the mode 

 of development, the past history, and the probable origin of 

 the great World of Life of which we form a part, which 

 encloses us in its countless ramifications, and upon whose 

 presence in ample quantity we depend for our daily food 

 and continued existence, we have perpetually to discuss and 

 to deal with those entities technically known as species, but 

 which are ordinarily referred to as sorts or kinds of plants 

 and animals. When we ask how many kinds of deer or of 

 thrushes, of trout or of butterflies, inhabit Britain, we mean 

 exactly the same thing as the biologist means by species, 

 though we may not be able to define what we mean so 

 precisely as he does. 



Many people imagine, however, that Darwin's theory 

 proves that there are no such things as species ; but this 

 is a complete misconception, though some biologists use 

 language which seems to support it. To myself, and I 

 believe to most naturalists, species are quite as real and 

 quite as important as when they were held to be special 

 creations. They are even more important, because they 

 constitute the only definite, easily recognised, and easily 

 defined entities which form the starting-point in all rational 

 study of the vast complex of living things. They are now 

 known to be not fixed and immutable as formerly supposed ; 

 yet the great mass of them are stable within very narrow 

 limits, while their changes of form are so slow, that it is only 

 now, after fifty years of continuous search by countless 

 acute observers, that we have been able to discover a very 

 few cases in which a real change — the actual production of 



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