THE SWIiUHNG, OR NATATORIAL GROUP. 153 



and in others the -windpipe makes singular 

 loops or flexures before entering the cavity of 

 the chest to merge into tlie lungs. 



In a state of nature, the males and females 

 pair, the young are hatched, covered with 

 down, and soon take to the water under the 

 guidance of their parents. With respect to 

 food, it is very various ; some appear to be 

 herbivorous, others feed equally npon animal 

 and vegetable substances, and greedily devour 

 slugs, caterpillars, and aquatic insects. Others 

 live on crabs, and marine shellfish, which they 

 dive with great skill to obtain. 



Though these birds are aquatic in their 

 habits, and swim well, yet some are much 

 more so than others ; the goose, which grazes 

 on corn lands and fields, is far less aquatic 

 than the wild or even tame duck, and resorts 

 to the water principally for safety. The cere- 

 opsis goose of Australia is still more decidedly 

 terrestrial. On the other hand, some species, 

 as the New Holland musk duck, the steamer, 

 or racehorse duck of the Falkland isles, and 

 others, are as aquatic as the divers (Colymhus.) 



jMost, if not all the anatidee, in the northern 

 hemisphere at least, are migratory, and asso- 

 ciated in flocks perform at due times northward 



