Evaporation, and plant societies, 90 and soil moisture, 62 open and wooded areas, 91 plant societies and, 64 Evolution, 9 and adaptation, 97 as a process, 10 ecological features of, 21 experimental, 96 mutual aid a factor of, 133 of life and _Salpa_, 123 organic, and baseleveling, 86 Existence, natural conditions, 96 struggle for, 2, 122, 123 Experiment Station Record, 76 Experimental evolution, 96 Experimental morphology, 95 Experimental study, limits, 103 Experimental zoölogy, 96 Explanatory or developmental method, 14, 15 Exploration, scientific, 63 External relations, 1 Extremes, influence, 98 Eyes, frog, 110 insects, 110 slug, 110 snail, 110 sow bug, 110 various types and image-forming powers, 110 worms, 110 Factor of evolution, mutual aid a, 133 Factors, influence of the slowest, 98 limiting, 98 Family, 132 Fauna, and flora of the sea bottom, 64 cave, 101, 112, 143, 144, 145 cryptozoic of Australasia, 144 Germany, classified by habitat, 134 grave, 144 Indiana caves, 144 Mayfield’s Cave, 143 of brackish waters of Lower Elbe, 138 of Kiel Bay, 138 pond, 148 quantitative determination in brackish waters, 137 salt water, 111 Faunal significance of baseleveling, 86 Feeding habits, slugs, 125 snails, 125 _Venus mercenaria_, 114 Feeding reactions of rose coral, 109 Feeding reflexes of shell-fish, 114 Fertilization of flowers, 142 Field ants, 149 Field naturalist, 37 Field notes, 42 numbers in, 50, 51 recording, 42 Field study, 36, 37, 38 plan, 36 Field work, primary aim, 41 Fish, associations of a lake, 147 associations of Illinois, 140 distribution, 64 ecological succession, 133 environment and distribution, 64 environment, index to, 118 feeding grounds, affected by vegetation, 90 food, 76, 123 food relations of fresh-water, 123 habitats of Illinois, 140 habits, 63, 112 Illinois, 140 lateral-line organs of, functions, 116 life histories, 112 marine vegetation, 89 metabolism, 100 methods of study, 39 of a small stream, 147 organ of sense, 113 organ of taste, 113 physiological responses of, 112 pond, 133 productivity in standing and running water, 101 reaction to atmospheric gases in water, 118 reaction to carbonic acid, 118 reaction to oxygen, 118 rheotropism in, 115 sense of hearing, 116 spawning habits of, 112 stream, 133 submerged vegetation affecting feeding ground, 90 Fitness of environment, 85 Floods of lower Danube affecting biological conditions, 145 Florida mangroves forming animal habitats, 89 Flowers, and insects, 142, 143 animal visitors, 141, 142 bees and, 141 fertilization, 142 pollination of, in relation to animals, 141, 142