428 



ANIMAL AGGREGATIONS 



Riley, C. F. C, 52 



Riley, C. V., 330 



Robertson, T. B., 120, 122, 138, 161, 162, 

 163, 164, 165, 166, 167, 168, 170, 

 172, 173, 176, 178, 180, 216, 218, 

 235, 248, 249, 250, 252, 354 



Robertson's phenomenon, in Protozoa, 

 161, 178 

 in TriboUum, 178, 180 



Robin roosts, 28, 80, 339 

 postbreeding-season flocks, 343 



Roosts of birds, 28 

 Root, F. M., 33 

 Root excretions, 103 

 Rophalosiphum, see Aphids 

 Rossman, B., 97 

 Roux, W., 45, 46 

 Russell, E. J., 103 

 Ruthven, A. G., 68 



Salamanders, 21 



spring migration, 67 



eggs, 358 

 Salmon, 21 

 Salpa chains, 16, 311 

 Salts, KCl, crowding and resistance to, 

 139, 209 



metallic, mass protection from, 213 



CaCL, KCN, NaCl, crowding and 

 resistance to, 215 

 Sarcina food for Colpidium, 166 

 Sarles, M. P., 135 

 Scale insect, mass relations, 240 

 Schistocerca, see Grasshoppers 

 Schizoneura, see Aphids 

 Schjelderup-Ebbe, T., 34, 129, 343, 344, 



345 

 Schnigenberg, E., 116, 118, 119 

 Schools, of fish, survival valve, 36 



analysis of young Amciurus, 62 



Schrittky, C., 75 



Schiicking, A., 264, 266 



Schuett, J. F., 202, 231, 258 



Schulz, R., 20, 25, 28, 61 



Schwarz, E. A., 75 



Sclater, W. L., 349 



Scyphozoa, strobila, 16 



Sea anemones, 16, 358 



crowding on growth form, 311 



Sea-urchin larvae, growth, inhibited by 

 crowding, 117, 153 

 promoted by crowding, 153 

 eggs, development hastened by crowd- 

 ing, 156 

 mass protection, from KCN, 215 

 of sperm, 218, 219, 263, 264, 267, 

 272, 274, 276, 278, 279, 281 ' 



egg secretions, effect on sperm, 272, 278 

 Sea urchins, 358 



distance sperm travel, 289 

 Sea-water, hypotonic, protection against, 

 222 

 heterotypic protection against, 228 

 factors contributing to, 231 

 Seals, mixed families, 27 

 herds of males, 28, 348 

 Segmentina, mass protection from col- 

 loidal silver, 211 

 Selous, F. C, 73 

 Seminal fluid, function, 263 

 Semper, K., 108, 109, 115, 117, 118, 191, 



248, 354 

 Sentinels, 346, 349 

 Seton, E. T., 28 

 Severin, H. C., 52 

 Severin, H. H. P., 52 

 Sex, importance of, 4, 337, 340, 341, 347, 



350 

 as basis of societies, 24, 26, 29, 87 

 ratio in Aselhis aggregations, 55 

 relations in "sleep" aggregations, 75, 



78, 80 

 factors in sex recognition, 89, 92 

 determination influenced by crowding, 



289 

 influence of crowding on, 289 

 in monstrillid copepods, 290 

 in Bonellia, 294, 309 

 in Crepidiila, 295, 309 

 in nematodes, 299, 309 

 in Cladocera, 303, 309 

 determination of, 289, 309 

 origin of, 290, 337, 351 

 promiscuity, 347 

 Sexual egg production in Cladocera, 303, 



306 

 Shackleford, M. W., 4, 8 

 Shaw, G., 113, 116, 119 

 Shelley, F. C, 305 

 Sherman, A., 92, 342, 343 

 Shull, A. F., 93, 313, 314 

 Siamang, 347 



