INDEX OF SUBJECTS 



36; 



Owl, screech, 229. 



Oxygen: anaerobic animals, 133; bur- 

 rowing dragon-fly nymphs, 142; circu- 

 lation of, 61; correlated with age of 

 ponds, 68-70; in lakes, 125, 133; in 

 pools, 91; in springs, 93; in streams, 

 103; intermittent quantities, 90; neces- 

 sary in water, 59; not added by certain 

 plants, 65; reduced by sewage, 17. 



Panther, 15, 238, 242. 



Partridge, 196. 



Perch: pirate, 120; yellow or American, 

 85, 99, 119, 120, 126, 130, 156; trout- 

 perch, 84. 



Pest species, number of, on different 

 forest trees, 166. 



Pewee, wood, 242, 244. 



Phalangids, 167. 



Physiological agreement of communities: 

 34; life histories, $^; proportionality 

 in organisms, 26. 



Physiological equilibrium: 26; distrib- 

 uted by changes in the organism, 30, 

 by external conditions, 30; in relation 

 to habitat, 31. 



Pickerel, grass, 105, 115, 142, 156. 



Pike: 85, 115, 120, 140; pike-perch, 85; 

 wall-eyed, 85. 



Pintail, 171. 



Planarians, in Lake Michigan, 77. 



Plankton: in arctic seas, 66; proportion 

 to denitrification, 66; relation to tem- 

 perature, 66, to C0 2 , 67, 68, to oxygen, 



67, 68, to carbonates, 67, 68, to rate of 

 flow, 67, to seasons, 67, to age of ponds, 



68, to moon, 67. 



Plants, aquatic: in sandy riffles, 99; in 

 sluggish streams, 104; value of, to 

 animals, 65, 142; watercress, 93. 



Plants, aquatic, scientific names: 



— Chara, 64, 65, 74, 142, 145, 148. 



— Cladophora, 64, 74. 



— Elodea, 65, 129. 



— Equisetum, 65, 151. 



— Myriophyllicm, 65, 129, 130, 131, 145. 



— Nostoc, 74. 



— Potamogeton, 145. 



— Proserpinaca, 151. 



Plants, terrestrial, scientific names: 



— Arabis lyrata, 228. 



— Citrus, 257. 



— Gossypium, 257. 



— Hibiscus, 189. 



— J uncus balticus, 173. 



— Monarda, 228, 232. 



— Opuntia, 255. 



— Pamassia caroliniana, 182. 



— Pinus banksiana, 228. 



■ — Sagittaria, 175. 



■ — Tilia, 257. 



Plover, piping, 180. 



Polyzoa, scientific names: 



— Fredericella sultana, 84. 



— Paludicella ehrenbergii, 84. 



— Pectinatclla magnifica, 128, 130, 135. 



— Plumatella, 84, 103, 121, 131: 

 polymorpha, 135. 



Polyzoan, gelatin-secreting, 128, 129. 



Pond animals in streams, 102, 103. 



Pond communities: 136-57; temporary, 

 173-80. 



Ponds, vernal or temporary: forest, 179; 

 snails of, 192; influence of rainfall on, 

 177-79; vegetation choked, 174; young, 

 with bare bottom, 173. 



Porcupine, Canada, 196. 



Prairie chicken, 167, 289. 



Prairie communities, 278-98. 



Pressure of water, 64. 



Protected situation of large lake, com- 

 munities of, 80. 



Protection of wild animals: 8-1 1; pro- 

 tected species, 56, 57; wardens, 57. 



Proteid, foodstuffs, 66. 



Protozoa: 129, 130; anaerobic, 133; 

 as animal food, 20; producers of disease, 

 20. 



Protozoa, scientific names: 



— Actinophrys sol, 75. 



■ — Difflugia: 



globulosa, 75. 

 pyriformis, 132. 



— Peridinium tabulatum, 75. 



Psocus, 234. 



Pulmonate snails, aquatic respiration 

 of, 129. 



Pumpkin-seed, 84, 156. 



Puss caterpillar, behavior of, 232. 



Quantity: of larger animals, 69; of life 

 on land, 166; of plankton: causes of 

 fluctuations in, 72; in different bodies 

 of water, 67; in ponds of different 

 ages, 69; in polar regions, 66; seasonal 

 variation in, 67. 



Rabbit: 196; cottontail, 269, 275. 

 Raccoon: 199, 202; eats crayfishes, 90. 



