40 ESSAY ON CLASSIFICATION. Part I. 



as distinct species, must have had from the beginning a different and distinct 

 geographical range, frequently occujjy sections of areas which are simultaneously 

 inhabited by the representatives of other species, which are perfectly identical over 

 the whole area. By way of an example, I would mention the European and the 

 American Widgeon, [Anas '3Iarcca ' Penehjje and A. ainericmm,) or the American and the 

 European Red-headed Ducks, (A. ferina and A. eri/throcephah,) which inhabit respectively 

 the northern parts of the Old and New World in summer, and migrate further south 

 in these same continents during winter, while the Mallard {A. BoscJias) and the Scaup 

 Duck (yl. marila) are as common in North America as in Europe. What do these 

 fixcts tell : That all these birds originated together somewhere, where they no longer 

 occur, to establish themselves in the end within the limits they now occupy ? — or 

 that they originated either in Europe or America, where, it is true, they do not hve 

 all together, but at least a part of them ? — or that they really originated within the 

 natural boundaries they occupy? I suppose with sensible readers I need only argue 

 the conclusions flowing from the last supposition. If so, the American Widgeon and 

 the American Red-headed Duck originated in America, and the European Widgeon 

 and the European Red-headed Duck in Europe. But what of the Mallard and the 

 Scaup, which are equally common upon the two continents; did they first appear in 

 Europe, or in America, or simidtaneously upon the two continents ? Without entering 

 into further details, as I have only desired to lay clearly a distinct case before my 

 readers, from which the character of the argument, which applies to the whole animal 

 kingdom, may be fully understood, I say that the facts lead, stejj by stejD, to the 

 inference, that such birds as the Mallard and the Scaup originated simultaneously and 

 separately in Europe and in America, and that all animals originated in vast num- 

 bers, indeed, in the average number characteristic of their species, over the whole of 

 their geographical area, whether its surface be continuous or disconnected by sea, 

 lakes, or rivers, or by differences of level above the sea, etc. The details of the 

 geographical distribution of animals exhibit, indeed, too much discrimination to admit 

 for a moment that it could be the result of accident, that is, the result of the 

 accidental migrations of the animals or of the accidental dispersion of the seeds of 

 plants. The greater the uniformity of structure of these widely distributed organized 

 beings, the less probable does their accidental distribution appear. I confess that 

 nothing has ever surprised me so much as to see the perfect identity of the most 

 delicate microscopic structures of animals and plants, from the remotest parts of the 

 world. It was this striking identity of structure in the same types, this total inde- 

 pendence of the essential characteristics of animals and plants, of their distribution 

 imder the most extreme climatic differences known upon our globe, which led me to 

 distrust the belief, then almost universal, that organized beings are influenced by 

 physical causes to a degree which may essentially modify their character. 



