244 DARWINIANA. 



Facts like these, which suggest grave diversifica- 

 tion under long lapse of time, are well supplemented 

 by those which essentially demonstrate a slighter 

 diversification of many species over a wide range of 

 space ; whether into species or races depends partly 

 upon how the naturalist uses these terms, partly upon 

 the extent of the observations, or luck in getting to- 

 gether intermediate forms. The researches of Prof. 

 Baird upon the birds of this continent afford a good 

 illustration. A great number of our birds which 

 have been, and must needs have been, regarded as 

 very distinct species, each mainly with its own geo- 

 graphical area, are found to mingle their characters 

 along bordering lines ; and the same kinds of differ- 

 ences (of coloration, form, or other) are found to pre- 

 vail through the species of each region, thus impress- 

 ing upon them a geographical facies. Upon a sub- 

 mergence of the continent, reducing these several 

 regions to islands sufficiently separated, these forms 

 would be unquestioned species. 



Considerations such as these, of which a few speci- 

 mens have now been adduced (not general specula- 

 tions, as the unscientific are apt to suppose), and trials 

 of the new views, to see how far they will explain 

 the problems or collocate the facts they are severally 

 dealing with, are what have mainly influenced work- 

 ing naturalists in the direction of the provisional 

 acceptance of the derivative hypothesis. They leave 

 to polemical speculators the fruitless discussion of the 

 question whether all species came from one or two, or 

 more ; they are trying to grasp the thing by the near, 

 not by the farther end, and to ascertain, first of all, 



