166 ZOOLOGICAL GARDENS. 



under the generic name of Anas, derived originally from 

 the Common Duck, and extended from it to the whole 

 of its tribe. But the vast number of species thus 

 brought together, and the consequent difficulty of de- 

 termining any unknown bird that might be referable 

 to the group, long since suggested the expediency of 

 its dismemberment, and the formation of smaller and 

 more manageable subdivisions. Many naturahsts, from 

 Ray down to the present time, have attempted, with 

 more or less success, to simplify by these means the 

 study of the most interesting family among our Water- 

 fowl ; but several of the divisions that have been estab- 

 lished among them rest upon such apparently trivial 

 characters, that we are by no means prepared to adopt 

 them in their fullest extent. There are some, however, 

 such as the Swans, the Geese, and the Ducks, so 

 strikingly distinguished, as to have been separated, in 

 popular nomenclature, from the earliest times ; and this 

 separation being confirmed by tangible characters, we 

 cannot hesitate to consider it as founded upon just and 

 sufficient principles. 



Of the characters by which the Swans are distin- 

 guished from the rest of the family, the most remarkable 

 are the extreme length of their necks ; the oval shape 

 of their nostrils, which are placed about the middle of 

 their bill ; the nakedness of their cheeks ; the equal 

 breadth of their bills throughout; the great depth of 

 that organ at the base, where the vertical considerably 

 exceeds the transverse diameter; and the position of 

 their legs behind the centre of gravity. They are by 

 far the largest species of the family ; and there are very 

 few birds that exceed them in magnitude. They live 

 almost constantly upon the water, preferring the larger 

 streams and open lakes ; and feed chiefly upon aquatic 

 plants, the roots of which they are enabled to reach by 



