POLISH SWAN. 117 



consider immutahilis to be a good species, only an albino 

 variety of the common mute swan. That of a brood of cygnets 

 in Holland half the number were grey and the other half 

 white, from the egg, and this opinion had so much weight 

 with Mr. Gurney that he abandoned his intention of bidding for 

 the living pair. As you are probably aware, the Ornithological 

 Society of London bought, some years ago, a male, temale, and a 

 young white bird of this immutahilis. The female and the young 

 bii'd died some time afterwards, but the old male would never breed 

 or even associate with any of the tame female swans. Lord Derby had 

 also a pair of this immutahilis, but his male bird died, and early in 

 the year 1850, his Lordship wrote to ask me to use my influence with 

 the Council of the Ornithological Society here, to obtain for him the 

 old male to pair with his solitary female, his Lordship giving us 

 other water birds in exchange. This was immediately agreed to, 

 the male bird was sent down, and a commission sent by me pro- 

 duced for us at the sale this very pair of birds which Mr. Gurney 

 declined bidding for. They are now on the water in St. James' 

 Park. * * * * The birds have not the character 

 which distinguish Albinos as varieties, and I have very little doubt 

 that one of the parents of the brood Mr. Westerman referred to 

 was a true immidahilis. 



The albino theory tlius mooted by Dr. Westerman 

 has since been adopted by others as a satisfactory expla- 

 nation of the so-called Polish swan having white cygnets ; 

 but whilst Yarrell's supposition is a fair one, that in the 

 case cited by Westerman of a mixed brood of grey and 

 white cygnets one of the parent birds may have been 

 immutahilis, I cannot concur in the idea of albinism, 

 from the absence of any evidence, so far as I know, 

 of Cygnus olor ever having white cygnets either in a 

 wild state, or when nesting on our rivers and broads, 

 and in a still closer state of domestication, on orna- 

 mental and circumscribed pieces of water. No such 

 variation, so far as I can ascertain, was ever known to 

 our local swan-herds from their own experience or by 

 tradition ; indeed, the only exception to the usual 

 colouring of the cygnets of the mute swan (p. 79) I have 

 any note of was rather a melanism than otherwise. 



