X TABLE OF CONTENTS 



CHAPTER XV 



PAGE 



THE CRAYFISH . 130 



Habitat (130). Means of protection (130). Sensitiveness 

 to surroundings (132). Locomotion (133). Food and di- 

 gestion (133). Absorption and circulation (134). Respira- 

 tion (134). Reproduction (134). Relations to man (135). 



CHAPTER XVI 



CRUSTACEA IN GENERAL .137 



Crabs (138). Barnacles (139). Fresh-water Crustacea ( 1 40) . 

 Relations of Crustacea to man (142). Value of Crustacea 

 as food for fish (142). Injuries due to Crustacea (143). 

 Characteristics and classification (143). 



CHAPTER XVII 

 THE MUSSEL OR CLAM AND OTHER BIVALVES . . . -145 



Habitat (145). Locomotion (146). The protective shell 

 (146). Structure of the shell (148). Movement of valves 

 of shell (148). Water current in the mussel (148). Principal 

 parts of the body (149). Respiration (149). Sensitiveness 

 to the surroundings (150). Digestion (150). Circulation 

 (151). Reproduction (151). The oyster (153). Soft-shell 

 clam (155). Razor-shell clam (156). Hard-shell clam (156). 

 Scallop (156). Classification of mussels and clams (157). 



CHAPTER XVIII 



A LAND SNAIL AND OTHER MOLLUSKS 158 



Life on land (158). Protection (158). Locomotion (159) 

 Sensitiveness to surroundings (160). Method of feeding 

 (160). Respiration ( 1 61). Slugs (161). Fresh-water snails 

 (162). Marine gastropods (163). Cephalopods (165). The 

 relations of mollusks to man (166). Characteristics and 

 classifications of mollusks (167). 



CHAPTER XIX 

 THE EARTHWORM AND OTHER SEGMENTED WORMS. . .168 



Need of moisture (168). Burrows (168). Locomotion 

 (168). Food (171). Digestion (171). Circulation and ex- 



