^^^^ THE NEW EVOLUTION "^1^ 



Many are colonial, forming incrustations on rocks or long chains 

 or hollow cylinders which float about suspended in the water. 

 Some of the bottom living types are raised on a long slender 

 stalk. In many the tough outer covering is largely composed 

 of cellulose, a substance especially characteristic of plants. 

 Many are very brilliantly phosphorescent. (Figs. 56-59, p. iii.) 



Phoronidea. — A very small group including less than ten 

 species, found only in the sea where the) are widely distributed, 

 but very local. (Fig. 101, p. 175, young.) 



SiPUNcuLoiDEA. — A small group, entirely marine, but very 

 widely distributed. 



MoLLuscA — the mollusks. — A very large and much diversified 

 group including the snails, slugs, clams, oysters, shipworms, 

 sea-butterflies, squid, octopus, nautilus, and many other types, 

 which are represented by a total of about fifty thousand species. 

 Most mollusks live in the sea where they are especially character- 

 istic of shallow w^ater, but a few are found in very deep water 

 and some in fresh water and on land, occurring even above the 

 snow line in the Himalayas. A number are parasitic, a few in 

 the larval stage only; others as adults are internal parasites, 

 lacking a shell and a digestive system. (Figs. 33, 34, p. 55; 

 45-52., p. 97; 74, p. 12.7; 95, p. 175.) 



Annelida — fbe jointed worms. — A large and much diversified 

 group including the earthworms, sea-worms, etc. Most of the 

 jointed worms live in the sea, but the earthworms and the ony- 

 chophores (Feripatus and its allies) live on land, and quite a 

 number, mostly allied to the earthworms, live in fresh water. 

 Some are free swimming, others live in mud or sand or in holes 

 in rocks or coral heads, and many construct limy or horny and 

 quill-like tubes. Many live in the cavities of sponges, and one 

 of these is branched, with a head on the end of every branch. A 

 few marine forms are parasitic, some being internal parasites, 

 chiefly in echinoderms. (Figs. 65, p. iii; 84, 85, p. 161; 104, 

 108, p. 175.) 



Brachiopoda — the lamp-shells. — A small group including about 

 170 species all of which live in the sea mostly in shallow water 

 or in water of moderate depth; but a few live in very deep water. 

 (Fig. 60, p. III.) 



Arthropoda — the jointed-legged (literally, footed) animals. — 

 This group includes the insects, spiders, scorpions, mites, crusta- 



