ON THE SPECIFIC DISTINCTION OF THE BRIDLED GUILLEMOT* 2I'J 



are distinct. In some species every possible variation of colour and marking 

 exists, as for instance in the Buzzard and the Crossbill, the Ruff and others. 

 Great, too, are the differences in very many species in the summer and 

 the winter plumage; manifold also the shades of pied varieties, from the 

 perfect albino down to the unfortunate bird, sure to be shot, that shews 

 a single "white feather." But I repeat, such variations are of a totally 

 different character from that of the case before us. Here we have a per- 

 nanent, distinctive, and always uniform mark of difference — "Quod semper, 

 quad ubique, quod in omnibus" — "semper idem." And, to come to the point 

 to which I have already briefly adverted, we have instances of a precisely 

 similar kind in other species where no possible doubt is or can be, at least 

 none is, entertained. One of these, that to which I have already more 

 particularly alluded, as having occurred to me, is that of the Crow, (Cor- 

 vus corone,) and the Hooded Crow, (Corvus comix,) which two birds are so 

 exactly or so closely alike in all but the colour of parts of the plumage, 

 that it would be impossible, or next to impossible, to distinguish them by 

 any other than that external mark. True, indeed, their habits are different, 

 the Crow, (C. corone,) being a solitary bird, only few being at times col- 

 lected together to feed on a common carrion, while the Hooded Crow, 

 (G. comix,) is decidedly gregarious; but not only in an enquiry into specific 

 distinctions do we look first to external or internal marks, and postpone 

 the consideration of the habits, but even these last, if mainly considered (even 

 though there should be a close resemblance,) might very likely lead us astray, 

 as in the case of the Black-backed Gull, (Larus marinus,) where we find 

 the young bird, the Wagel, collecting together in numbers, but the old 

 birds keeping aloof, singly, or at most, generally, in pairs, seldom more 

 than a pair being seen together. And it is not merely that it is the young 

 birds that .thus keep together as the members of a family, for we see 

 many more than these in a flock, the eggs being only three in number, 

 and that without the presence of the parents, as is the case in other con- 

 tinuances of the family union, and, moreover, I believe, until the full 

 assumption of the adult plumage, probably the third year. 



In a paper, entitled "Remarks upon the Ringed Guillemot," read before 

 the Natural History Society of Glasgow, by Robert Gray, Esq., and for- 

 warded to me by that gentleman for insertion in "The Naturalist," he 

 quotes from a statement made by J. Wolley, Esq. to the British Associ- 

 ation in the year 1850, that in the Ferroe Islands the two species, Troile 

 and lachrymans breed together promiscuously, in the proportion of one to 

 ten; on which a writer, E. K. B., in a subsequent letter to me as the 

 editor, observes, that it is left doubtful whether it is meant that the two 

 species breed together actually, or merely in the same situations, a decision 

 of which question would appear to decide the fact, pro or con the specific 



