ANIMAL LIFE IN THE SEA 163 
tropical part of the Atlantic, and in shallow bays or 
lagoons. Though both spend their whole life in the 
water, and are helpless outside it, yet both are definitely 
littoral, for they feed upon the large algae, and could 
therefore find no food in the open sea. The manatee 
apparently takes a large variety of aquatic plants in 
addition to algae. The animals are not nearly such good 
swimmers as the Cetacea, and their heavy bodies and 
massive bones fit them for life near the bottom. The 
hind-legs are entirely absent, but the fore-limbs may 
touch the ground as the animals swim leisurely along 
the bottom, and are also used in pushing food into the 
mouth, and in carrying the young, which are suckled 
above water. 
Of the littoral birds perhaps the most interesting are 
the flightless penguins, which present the same features 
as the seals in that, though pelagic for much of the year, 
and having a perfect mastery of the water, they must 
come on shore for breeding purposes. The absence of 
any carnivorous land mammals in the Antarctic area, 
and its inaccessibility, make it a perfect paradise for the 
penguins, who resort to its rocks and beaches in millions 
to breed, and have been described by all the Antarctic 
expeditions (see Fig. 44). Quite comparable in habits, 
though not related, was the extinct great auk (Alca 
umpennis) of the shores of the North Atlantic, which 
was similarly incapable of flight, and fell an easy 
victim to man during the breeding-season. 
Of the other birds which feed in the sea and frequent 
it, some, like certain of the seagulls, forsake it at the 
breeding-season for inland regions. Others, like little 
auks, guillemots, puffins, gannets, and so forth, breed 
on the shore, choosing cold or inaccessible regions 
for the purpose. Of the various adaptations to such 
L2 
