2i6 ANIMALS OF LAND AND SEA 



fishes and the ganoids, live wholly in fresh water, or at least 

 do so when young. 



Numerous mammals, like otters, feed wholly in the water, 

 others partly, some occasionally; the sea otter in the ocean 

 represents the otters of fresh water, but most of the water 

 feeding mammals of the land are not represented in the sea, 

 though they may frequent the sea shores on occasion and some- 

 times fish in quiet backwaters. 



Fresh waters have their share of water birds, of all the larger 

 groups except the petrels and their allies, tropic-birds, frigate- 

 birds, and some minor types; and there are other insect-feeding 

 water birds pecuUar to streams and lakes, like dippers and jac- 



anas. 



There are very many curious features connected with certain 

 creatures in fresh water. A few fish, amphibious, move from 

 pond to pond at night, and in the eastern tropics one sometimes 

 sees them in the roadways. Some sea fish also hop about on 

 mud flats, Uke ungainly frogs. In the dry season some fish 

 burrow in the mud and hibernate in a large mud cocoon. One 

 arctic fish lives frozen stift" throughout the winter months. 



The phenomenon of phosphorescence so striking in the sea 

 and so widely distributed in all the animal types is wholly 

 lacking in fresh water where only the aquatic larvae of some 

 fire-flies give out a light. The curious larval stages which are 

 such an interesting and instructive feature of the life of most 

 sea animals are shortened or entirely omitted in their fresh wa- 

 ter representatives. 



