458 ON THE MEALY LINNET. 



It is needless to remind the reader that the supposition last advanced, in- 

 volves the possibility of numerous existing races, or species, being derived from 

 a plurality of original stocks ; and the variableness of the American Nightherons 

 may thus, it is not unlikely, have originated in the admixture of a smaller race, 

 perhaps the European. So likewise the anomalous irregularity in the number of 

 tail feathers in Bewick's Swan — eighteen or twenty — may indicate that two 

 primitive races have become united ; which is the more probable, in this instance, 

 as, over and above certain other discordances which I have noticed in individuals 

 of the same sex and parentage, the Cygnus Bewickii, as now existing, inhabits 

 alike America and Europe, whereas the Hooper Swan, which is peculiar to the eastern 

 continent, is represented by an analogous but obviously distinct race in the western, 

 namely the Trumpeter Swan (C. buccinator), which has not hitherto been observed 

 elsewhere. That many scarcely distinguishable races, however, do, at the same 

 time, exist in the very same districts, apparently without intermixing, is a fact 

 that has been already sufficiently descanted on. 



Now the general corollary on all the foregoing detail, I conceive to be a fair 

 inference (of what is necessarily incapable of demonstration) that many true 

 species, or originally-created races, exist, which it is utterly impossible to distin- 

 guish — a conclusion of startling consequence to the student of Geology. It will be 

 sufficient to mention one additional case, wherein probability strongly militates 

 against the supposition of identity, but in which the most scrupulous comparison 

 fails to detect a single differential character to bear out the suspicion. — I allude 

 to the Common Cormorants of Europe and America. The birds of this genus, 

 though remarkably powerful on the wing, and capable of long continued exertion, 

 besides being able to recruit themselves by alighting on the water, are notwith- 

 standing only met with in the near vicinity of land ; and it would consequently 

 be inferred, that, of races inhabiting the Atlantic coasts of Europe or America, 

 those of which the range extended farthest northward would be the most likely 

 to occur on both continents ; yet such is not found to be the case ; inasmuch as 

 P/ialacrocorax carlo, Auct., which becomes rare in the northern isles of Scotland, 

 and soon disappears along the Scandinavian coast, and which in America scarcely 

 reaches beyond the southernmost extremity of Labrador, is deemed to be identical 

 on both shores of the ocean, whereas the European Ph. cristatus, and the American 

 PL dilophus, two nearly-allied but evidently distinct species, both of which 

 extend to high northern latitudes, appear to be quite confined to their respective 

 continent, where each is very numerously diffused. 



I commenced this essay by entitling it a disquisition on the Mealy Linnet ; 

 but I have little now to say exclusively relative to that particular race, — Montes 

 parluriunt, §c. — It belongs to one of those intricate knotty groups of which I 

 have spoken, comprising a number of undefinable species ; though of which two, 



