44 ESSAY ON CLASSIFICATION 



some species which are scattered over very extensive areas occupy 

 disconnected parts of that area, other species closely allied to one an- 

 other and which are generally designated under the name of repre- 

 sentative species occupy respectively such disconnected sections of 

 these areas. The question then arises, how these natural boundaries 

 assigned to every species are established. It is now generally believed 

 that each species had in the beginning some starting point from 

 which it has spread over the whole range of the area it now occupies, 

 and that this starting point is still indicated by the prevalence or 

 concentration of such species in some particular part of its natural 

 area, which, on that account, is called its centre of distribution or 

 centre of creation, while at its external limits the representatives of 

 such species thin out, as it were, occurring more sparsely and some- 

 times in a reduced condition. 



It was a great progress in our science when the more extensive 

 and precise knowledge of the geographical distribution of organized 

 beings forced upon its cultivators the conviction that neither animals 

 nor plants could have originated upon one and the same spot upon 

 the surface of the earth and hence have spread more and more widely 

 until the whole globe became inhabited. It was really an immense 

 progress which freed science from the fetters of an old prejudice. 

 For now we have the facts of the case before us, it is really difficult 

 to conceive how, by assuming such a gradual dissemination from 

 one spot, the diversity which exists in every part of the globe could 

 ever have seemed to be explained. But even to grant distinct centres 

 of distribution for each species within their natural boundaries is 

 only to meet the facts half way, as there are innumerable relations 

 between the animals and plants which we find associated everywhere, 

 which must be considered as primitive, and cannot be the result of 

 successive adaptation. And if this be so, it would follow that all 

 animals and plants have occupied from the beginning those natural 

 boundaries within which they stand to one another in such har- 

 monious relations. ^^ Pines have originated in forests, heaths in 

 heathers, grasses in prairies, bees in hives, herrings in schools, buffa- 

 loes in herds, men in nations.*" I see a striking proof that this must 



^^Agassiz, "Geographical Distribution of Animals," Christian Examiner, XLVIII 

 (1850), 181-204. 



""Agassiz, "The Diversity of Origin of the Human Races," ibid., XLIX (1850), 110- 

 145. 



