4i8 



ANIMAL AGGREGATIONS 



Courtis, S. A., 67 



Cowbirds, 13, 341, 342, 343 



breeding behavior, 27 



mutualistic relations with cattle 29 

 Crabb, E. D., in, 112, 119 

 Crabs, 21 



hermit, 21 



relation to Hydractinia, 29 



Pinnixa, lives in mollusk burrows, 31 



Craig, W., 95 



Crampton, G. C, 122, 123, 124 

 Crayfishes, sex recognition in, 89 

 Crepidula, size relation to hermit crab 

 shell, 123 

 sex determination in, 295, 302 

 abundance, 358 

 Crew, F. A. E., 309 

 Crow roosts, 28, 8o 

 Crowd, group defense by, 102 



see Crowding 

 Crowding, see also Aggregations 

 Crowding- 

 affects sex determination, 289 

 in monstrillid copepods, 290, 309 

 in Bonellla, 291, 309 

 in Crepidula, 295, 309 

 in nematodes, 295, 309 

 in Cladocera, 303, 309 

 harmful effects on growth, of plai ts, 

 102 

 of bacteria, 103 

 of Protozoa, 107 

 of snails; 108, 123 

 of echinoderms, no, 117, 153 

 of Daphnia, no 

 of tadpoles, 112 

 of Hydra, 112 

 of Planar ia, 113 

 of fish, 113, 116, 117 

 summary of factors causing, 118 

 increased death-rate, and, 136 

 work of Drzewina and Bohn, 140 

 and contagion, 144 

 in Ophioderma, 205 

 in grasshoppers, 319, 329 

 in Drosophila, 332 

 increases rate of reproduction, 161 

 in tissue culture, 166 

 in Triboliurn, 178 

 menace of, 184, 203, 360 

 morphological effects, 311 



wing production in aphids, 313 

 in grasshoppers, 316 

 in Drosophila, 331 

 protection, from colloidal silver, 201, 

 222 



from toxic salts, 213 



from high temperature, 217 



from ultra-violet, 218 



from hypotonic sea- water, 222 



heterotypic, 228 



factors contributing to, 231 



survival values in insects, 236 

 protects, from desiccation, 182 



affects metabolic rate, 181, 184, 186 



Ophroderma from autotomy, 182, 

 189, 190 



bacteria, 253 

 in spermatozoa, 263, 284 

 retarding effect on reproduction, 120 



in Paramecium, 120 



in Stylonychia, 122 



in Daphnia, 126 



in hens, 126 



in Drosophila, 131 



in hookworms, 135 



in Cladocera, 306 

 stimulates growth, 147 



in tissue cultures, 149 



heterotypic, in tissue cultures, 151, 



157 

 in echinoderms, 153 

 stimulates rate of regeneration in tad- 

 poles, 148 



Crump, L. M., 138, 166, 167, 168, 169, 



173 

 Ctenophora, 12 

 Ciilicidae, swarms of males, 66 



breeding behavior, 66 

 Cumingia, distance sperm travel, 289 

 Cummins, H., 66, 67 

 Curran, H. R., 105 



Cutler, D. W., 138, 166, 167, 168, 169, 173 

 Cyanide, effect on sperm suspensions, 269 



see also KCN 

 Cylisticus, see Isopods, land, 

 Cytotropism, 45, 46 



Dampf, A., 330 



Daphnia, crowding, effect on growth, no, 

 312 

 effect on rate of reproduction, 126 

 loss of fertility, death and, 137 

 survival value of crowding, 141, 215, 



239 



chromosomes, 303 



asexual generations, 304 



male production, 305 

 Darter, rainbow, breeding behavior, 68 

 Davenport, C. B., no, 118 



