Danube and its delta, biology affected by floods, 145 Death feigning, _Belostoma_ (= _Zaitha_) _flumineum_ Say, 118 instinct, 113 _Nepa apiculata_ Say, 118 Ranatra, 113 Death of lower organisms, 97 Decrease of birds, 124 Describing environments, 45 Descriptive method, 14 Desert species, of Amphibians, 148 of reptiles, 148 Determination, of specimens, 49, 51 of specimens at museums, 52 Determined specimens, series of, 52 Development, 92, 93 ants, 120 effect of environment on mollusks, 100 environment, 45, 46 individual, 97 oysters, 112 optima, 94 problem, 98 Developmental or explanatory method, 14, 15 Digestion in cold-blooded vertebrates, influence of season and temperature, 100 Diptera, aquatic nematocerous, 75 catalogue of North American, 71 North American, catalogue, 71 Directions for collection, 39, 57 Directory, Naturalist’s, 53 Disadvantages of non-ecological surveys, 31 Diseases, mussels, 119 Distribution, fish, 64 Planarians, local, 119 vertically of Chætognatha, San Diego region, 115 Domestic animals, 132 psychic development of young, 115 Dominance, 47 Dominant animals, 47, 48 Donaciinæ, natural history of larvæ, 109 Dragon flies, _vs._ mosquitoes, 72 Dragon-fly nymphs, ecology, 118 keys, 75 reactions to contact and light, 118 Drinking habits, butterflies, 119 moths, 119 _Drosophila_, convulsive reflexes, 109 reactions, 109 Dunes, bee fauna, 139 Dynamic conceptions, 80 Dynamic principles, 86 Dynamic relation, 85 Dynamic relations, of aggregations, 130 of associations, 130 of environment, 82 Dynamic standpoint, 91, 101 Dynamic status, 29, 31 Dynamic theory and physiological problems, 97 Dynamical interpretation, 82 Dynamics of living matter, 96 Earthworm, behavior modifiable, 105 movements, 105 quantitative studies, 58 Echinoderms, food, 126 Ecological catalogue of crawfish, 113 Ecological criteria, 16 Ecological distribution of birds of Isle Royale, 148 Ecological features of evolution, 21 Ecological ideas, educational value, 146 Ecological organization of museums, 22 Ecological relations, of entomophilous flora and anthophilous insect fauna of Illinois, 142 of invertebrate fauna of Isle Royale, 146 Ecological study, of cave plankton, Shawnee Cave, 145 of lake plankton, 140 Ecological succession, 21, 90, 101, 124 birds, 124, 133 causes in ponds, 133 fish in ponds and streams, 133 land animals, 133 mammals of Isle Royale, 145 on an oyster reef, 112 Ecological surveys, 23, 24, 67 Ecological training for surveys, 32