192 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 

 Cygnus immutahilis Yare. 

 Polish Swan.* 



DiAGN. — Culmen until a smaller Jcnoh at the base; legs in the aclulls 

 slate-gray or yellowish gray ; young white ^ icith the bill light pinMsh red. 



Syn. — 1838.— Cygmis immutahilis Yarr., Proc. Zool. Soc. Lond. 1838, p. 19 (nee v. Pelz, 

 18(i2, quse C. unwini Hume), 



Since Yarrell, in 1838, described this species, but few contributions 

 to the ehicidation of the questions concerning its habitat and its rela- 

 tion to C. gibbus have been made. The time was when its right as a 

 species was generally denied, essentially for the reason that a few in- 

 stances of mixed broods with both white and gray cygnets were stated 

 to have occurred. But at present, the opinion being inclined to regard 

 such a case as "the result of an alliance between a Mute and a Polish 

 Swan," the distinction of these two species seems to be generally ad- 

 nntted — at least in England. The various investigations about this 

 question are described at great length, and important new observa- 

 tions given, by Mr. Dresser in his Birds of Europe, Parts Ixxvii, 

 Ixxviii, and Ixxix, April, 1880, but not even he has answered the in- 

 quiry as to the true habitat of the immutabilis. At first I regarded 

 it as an eastern form, confounding it with G. unwini; but I have now 

 convinced myself that the latter constitutes a different species, and I 

 am inclined to believe that the English immutahilis will show itself to 

 be a western bird. Specimens can easily be overlooked, and a few may, 

 perhaps, be found in one or another of the European museums (as, for 

 instance, the example in Mus. Leiden.), but I see no reason why it should 

 be supposed that the ornithologists of the continent have been less ex- 

 act in this case than those of England. I therefore regard the species 

 as being very scarce on the European continent; the only specimen 

 from there was killed in Holland, just opposite to England, in which 

 latter country it seems to be not even rare. 



Blainville has already questioned whether the immutabilis is not 

 the wild form of the Tame Swan, and we see that Mr. Dresser for a 

 long time also was inclined to indorse the same view, which, however, 

 my investigations most positively contradict, it appears to me that 

 the question, with more right, could be asked conversely, viz, whether 

 the Polish Swan is not a race originated by domestication ; but even 

 this seems not to be the case, as it appears from the quotation in Mr. 

 Dresser's Birds of Eur. (1. c.) of the experiences of Mr. SmpsoN, "who 

 had from seventy to a hundred cygnets through his hands yearly for 

 the past thirty years, and who never saw a white one," and f.om the 

 statement of Mr. Dresser himself, that the Changeless Swan, " so far 



*Not "Polar Swjiu (Cygne du Pole)" as Blainville, Compt. Reud. VII, 1838, p. 

 1024, and after him Degl. «fe Gerbe, Ornith. Eur. II, p. 477, indicates. 



