EXAMPLE: THE CRAYFISH (CAMBARUS SP.). Structure, 146.--Life-history and habits, 146. OTHER CRUSTACEANS. Body form and structure, 147.--Water-fleas (_Cyclops_), 148.--Wood-lice (_Isopoda_), 150.--Lobsters, shrimps, and crabs (Decapoda), 151.--Barnacles, 155. XXI.--BRANCH ARTHROPODA (CONTINUED). CLASS INSECTA: THE INSECTS. EXAMPLE: THE RED-LEGGED LOCUST (MELANOPLUS FEMUR-RUBRUM). [Laboratory exercise]. External structure, 157.--Life-history and habits, 161. EXAMPLE: THE WATER-SCAVENGER BEETLE (HYDROPHILUS SP.) [Laboratory exercise]. External structure, 163.--Internal structure, 166.--Life-history and habits, 169. EXAMPLE: THE MONARCH BUTTERFLY (ANOSIA PLEXIPPUS) [Laboratory exercise]. External structure, 171.--Life-history and habits, 175. EXAMPLE: LARVA OF MONARCH BUTTERFLY [Laboratory exercise]. Structure, 177. OTHER INSECTS. Body form and structure, 181.--Development and life-history, 188.--Classification, 191.--Locusts, cockroaches, crickets, etc. (Orthoptera), 192.--The dragon-flies and May-flies (Odonata and Ephemerida), 194.--The sucking-bugs (Hemiptera), 197.--The flies (Diptera), 201.--The butterflies and moths (Lepidoptera), 205.--The beetles (Coleoptera), 206.--The ichneumon flies, ants, wasps, and bees (Hymenoptera), 212. CLASS MYRIAPODA: THE CENTIPEDS AND MILLIPEDS. CLASS ARACHNIDA: THE SCORPIONS, SPIDERS, MITES, AND TICS. XXII.--BRANCH MOLLUSCA: THE MOLLUSCS. EXAMPLE: THE FRESH-WATER MUSSEL. (UNIO SP.) [Laboratory exercise]. Structure, 239.--Life-history and habits, 243. OTHER MOLLUSCS. Body form and structure, 245.--Development, 246.--Classification, 246.--Clams, scallops, and oysters (Pelecypoda), 246.--Snails, slugs, nudibranchs, and "sea-shells" (Gastropoda), 252.--Squids, cuttlefishes, and octopi (Cephalopoda), 255. XXIII.--BRANCH CHORDATA: THE ASCIDIANS, VERTEBRATES, ETC. Structure of the vertebrates, 259.--Classification of the Chordata, 260.--The ascidians, 261. XXIV.--BRANCH CHORDATA (CONTINUED). CLASS PISCES: THE FISHES. EXAMPLE: THE GOLDEN SUNFISH (EUPOMOTIS GIBBOSUS) [Laboratory exercise]. External structure, 263.--Internal structure, 265.--Life-history and habits, 270. OTHER FISHES. Body form and structure, 271.--Development and life-history, 276.--Classification, 277.--The lancelets (Leptocardii), 277.--The lampreys and hag-fishes (Cyclostomata), 278.--The true fishes (Pisces), 279.--The sharks, skates, etc. (Elasmobranchii), 279.--The bony fishes (Teleostomi), 281.--Habits and adaptations, 285.--Food-fishes and fish-hatcheries, 288. XXV.--BRANCH CHORDATA (CONTINUED). CLASS BATRACHIA: THE BATRACHIANS. Body form and organization, 292.--Structure, 293.--Life-history and habits, 295.--Classification, 297.--Mud-puppies, salamanders, etc. (Urodela), 297.--Frogs and toads (Anura), 299.--Cœcilians (Gymnophiona), 302. XXVI.--BRANCH CHORDATA (CONTINUED).