INDEX OF SUBJECTS 



357 



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, 33; 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 CO 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. 



Myriophyllum, 65, 129, 130, 131, 145. 



Nostoc, 74. 



Potamogeton, 145. 



Proserpinaca, 151. 



Plants, terrestrial, scientific names: 



Arabis lyrata, 228. 



Citrus, 257. 



Gossypium, 257. 



Hibiscus, 189. 



Juncus balticus, 173. 



Monarda, 228, 232. 



Opuntia, 255. 



Parnassia caroliniana, 182. 



Pinus banksiana, 228. 



Sagittaria, 175. 



Tilia, 257. 



Plover, piping, 180. 



Polyzoa, scientific names: 



Fredericella sultana, 84. 



Paludicella ehrenbergii, 84. 



Pectinatella magnified, 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-n; 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. 



