Incluye referencias bibliográficas (p. 553-557) e índice CONTENIDO: Introduction: sorting out living things -- Life activities -- Simple and complex protozoans -- Variations on a one-celled theme -- A side issue: sponges -- Two layers of cells -- Stinging-celled animals -- Comb jellies -- Three layers of cells -- New parts from old -- Messmates and parasites -- One-way traffic: proboscis worms -- Roundworms -- Lesser lights -- Soft-bodied animals -- Segmented worms -- Lobsters and other arthropods: crustaceans -- Arthropods on land: arachnids -- Airborne arthropods: insects -- Annelid-Arthropod allies -- Spiny-Skinned animals -- Chordate beginnings -- Records of the invertebrate past -- Invertebrate relationships -- Further knowledge.
