ANIMAL LIFE. 503 



especially such forms as the alligator and crocodile and the ancient 

 marine saurians, in reality we should think of them as primarily land- 

 inhabiting animals, some of which have gradually taken to aquatic life 

 aud in the course of time become more and more confined to a watery 

 sphere. Aquatic turtles show this most decidedly, an extreme being 

 found in the soft-shelled turtle, which is not only a constant resident 

 in water, but has become possessed of special organs for respiration in 

 water, so that air-breathing is scarcely necessary. Birds that live in 

 the water have taken the same convenient highway, and many of them 

 have traveled it from the time of their toothed ancestors down to the 

 present. Penguins have gone so far along this road that their wings 

 can no longer serve for flight, while loons and grebes and auks are on 

 the way. Gulls, albatrosses and petrels may go far out o'er billowy 

 wave hundreds of miles from land. Ducks and geese and swans have 

 struck the trail, and snipe, stork and heron, crane and flamingo have 

 rolled up their trousers and are wading in. Even the flsh-hawk, the 

 osprey and the eagle find it worth while to look beneath the wave. 



The aquatic habits of the beaver furnish a most remarkable exam- 

 ple of this, and if we could trace his acquisition of this habit from the 

 time when he must have been an ordinary terrestrial rodent with 

 neither a paddle-tail nor a web foot, we should certainly find an inter- 

 esting career. The musk-rat has not gone so far and can not reach 

 the same goal, as he has flattened his tail in the wrong direction. 



The whale — that giant of the seas — largest of mammals and indeed 

 of all animals, has out-traveled all his relatives in reaching out into 

 the great ocean, but we can not possibly conceive the whale to have 

 come from any other source or to have other ancestor than a land- 

 inhabiting mammal. We get glimpses of the mile posts he has passed 

 in the structures shown by the manatee, the walrus, the sea lions and 

 others. Not that these constitute in any sense his ancestral line, for 

 that was far back in time and so far largely a lost history. But along 

 such stages we must believe his ancestors to have passed. The manatee 

 in its way is as strictly aquatic as the whale but hugs the shore or rivei- 

 mouths. 



The hippopotamus is well on the way, and I would digress here to 

 call attention to the remarkable similarity in adaptation of the sense 

 organs of this animal to those of the alligator and crocodile. Note 

 that the eyes, ears and nostrils are almost exactly in the same plane 

 and so situated that they may all be above the surface of the water, 

 while practically no part of the head or body may be visible, an admira- 

 ble adjustment to avoid detection from foes or for protection against 

 flies, mosquitoes, etc. Seals, walruses, sea lions, sea otters and, in less 

 degree, the polar bear, the common otter and mink, all show aquatic 

 habit fixed or growing, and even the small boy at his favorite swim- 



