320 NATATORES. 



drift about when there is a considerable swell upon the 

 water, they prefer feeding when it is tranquil. The tame 

 swan requires no description, further than a reference to the 

 specific differences between it and the wild ones. The plu- 

 mage of the tame swan is white; the bill red, with the 

 tuberculated membrane at the base and the margins black. 

 The trachea is not enlarged or convoluted at the pulmonary 

 extremity. The length of the full-grown male is from four 

 feet to four feet and a half; the extent of the wings about 

 seven feet ; and the weight about twenty-five pounds. In 

 their mature plumage, there is no external difference of 

 appearance in the sexes. The nest is built of reeds and 

 sedges, on a dry spot near the water ; the eggs are from 

 five to eight ; and the incubation lasts about six weeks. 

 The female sits closely, and the male keeps guard the while 

 with much vigilance. In defence of their young they can 

 hit a very severe blow with the bend of the wing, much 

 more severe than they, who think merely of the mass, and 

 do not take into account the velocity which muscles of 

 flight are capable of producing, would be apt to suppose, 

 though perhaps not so great as has been alleged of a bird 

 with which authors have very generally been a little 

 poetical. 



The young are grey at first, and do not acquire their white 

 plumage till the second year. 



THE WILD, OR WHISTLING SWAN (Ci/gnus ferns). 



This species differs from the tame one both in its external 

 and its internal characters. Its bill is subcylindrical and 

 black, with the base and margin yellow, and the head and 

 nape have a slight yellowish tinge : the rest of the plumage 

 is white. The dimensions and weight are nearly the same as 

 those of the former species, only the wings are rather shorter 



