PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 193 



as he can ascertain, has only been recorded in a wild state from the 

 shores of Great Britain."* Should it, after all, be an absurd supposition 

 that immutabilis is the indigenous wild English Swan, while gibbus is 

 inctigenous only to the continent, but introduced, in a half domesticated 

 state, to England during the time of Richard I"? 



This Swan presents the peculiar fact that the young of it are better 

 distinguishable from its nearest allies than the adults of both species 

 in their perfect plumage. This is, however, no objection to its right to 

 be considered a species any more than in the case of two other species, 

 the plumages of whose young are quite alike. 



The most conspicuous distinctive mark of the two species is that the 

 young (in down and in the first plumage) of immutabilis are white, and 

 not gray or brownish, as in gibbus. They are, however, not pure white, 

 at least not always, as they were described as being on the back more 

 or less tinged with warm bufl*. 



They differ also in the color of the bill, this being pale pinkish red in 

 the young immntahiUs and i^lumbeous in gibbus. It cannot here be ob- 

 jected that the Mute Swan in the later youth also has the bill of a sim- 

 ilar color, as it, during the transition to the white plumage, begins to 

 take a reddish tone, because the mentioned red color on the bill of the 

 young Polish Swan is to be found already in the first summer simul- 

 taneous with the first feathers, as is evident from Mr. Soutwell's 

 (Dresser 1. c.) description of the plumage of three young the 20th of 

 August: "They had then assumed nearly all their feathers and were 

 more than half grown ; the color was white, apparently stained or sul- 

 lied by a yellowish tint, which was strongest on the wing-coverts; feet 

 pale ash-color, and beak a purplish flesh-color, differing entirelj^ from 

 the lead-color of the bill in the young Mute Swan of the same age." 

 Also the color of the bill of the adult birds is diftereut, the Polish Swan 

 having it rather redder than the continental species. 



The frontal knob is said to be smaller in immutabilis at all ages. It 

 is, however, present also in the quite young, as is evident from Mr. 

 Dresser's plate, fig. 2. The eye and the lamella, too, are said to be 

 smaller. 



The character now to be mentioned belongs only to the adult birds. 

 In the adult gibbus the legs are jet-black, sometimes with a shade of red 

 shining through the black color; in immutabilis their color is variously 

 stated to be from pale j)! mbeous or slate-gray to a light drab color. 

 This latter color they had in the specimen examined by me. In the 

 young the color of the feet is nearly the same in the two species, and it 



*I8 the statement, p. 4, about the captures of immutabilis in NorfolTc, enumerated by 

 Mr. Stevknson, contrary to this? He says: "Some, at least, if not most of these, 

 however, were undoubtedly birds Avhich had straggled from other waters, aud not 

 genuine wild birds." I cannot plainly see if these words are the refiectious of Mr. 

 Dresser himself or only a quotation of Mr. Stevenson. 



Proc. Nat. Mus. 82 13 Jwly S5, 1 882. 



