OP THE BEITISH ISLANDS. 307 



probably carried to such a height in anticipation of any sudden rise in' the water 

 near by. As incubation proceeds it often increases in bulk, the birds adding 

 materials from time to time. In Northern Eussia from two to four eggs form a 

 clutch ; in Iceland five are frequently found ; and old females are said occasionally 

 to lay as many as seven. The eggs are laid towards the end of May in some 

 districts, a fortnight later in others. They are creamy-white in colour, rough in 

 texture, and nearly oval in shape. They measure on an average 4'5 inches in 

 length by 2'8 inches in breadth. Incubation lasts from five to six weeks, and 

 according to Dr. Palmen the young mature slowly. One brood only is reared in 

 the year. 



Diagnostic characters.— Gygnus, with the tail short and rounded, and 

 with the lores and the basal portion of the bill extending below the nostrils 

 yellow, remainder black. Length, 60 inches. 



