"^"^ THE NEW EVOLUTION '^^^^ 



p. 97), fishes, whales and porpoises, while in the air 

 above live many sea-birds. 



Besides being almost as heavy as protoplasm and 

 thus rendering easily possible free floating or sus- 

 pended life, sea water is constantly in motion, though 

 in the deep sea this motion may become extremely 

 slow. This means that everywhere in shallow water 

 where the waves and tides create a constant movement 

 animals are able to attach themselves firmly to the 

 bottom (figs. 60, 63, 67, 68, p. iii;figs. 76, 80, p. 143) 

 or to root themselves or burrow in the mud and then 

 let the motion of the restless water do the work of 

 bringing food to them. 



In progressively deeper water where the motion 

 gradually becomes so very slight as almost to be 

 absent, the wanderings of suspended creatures en- 

 dowed with feeble locomotor powers render attached 

 existence for such larger creatures as are able to over- 

 come and feed on them just as advantageous as 

 attached existence is along the shores. 



So we are not surprised to find that various types of 

 animals which, attached firmly to the rocky bottom or 

 rooted in the mud, both grow and look like plants, 

 are especially characteristic of the sea. Such types of 

 animals are the corals (fig. 80, p. 143), sea-pens (fig. 

 77, p. 143), sea-fans, gorgonians, sea-squirts, hydroids 

 (figs. 75,76, p. 143) and sea-mosses (figs. Gj^ 68, p. iii), 

 belonging to a great array of different groups. More 

 familiar to us are the oysters, barnacles (fig. 30, p. 47) 

 and mussels, the mud-boring clams and razor-clams, 

 the sponges, and various sorts of encrusting and plant- 



[66] 



