INDEX 



421 



relation of animals to, 277; relation 

 of horse to, 328; relation of range to. 

 297; unstable, 287 



Environments, abundance of, 306; con- 

 ditions in, 294; differences in, 294; 

 major, 292; plant associations of (see 

 Vegetation) 



Enzymes, 49, 55, 68; classification of, 56 



Eocene, 319, 320, 321, 324, 325, 329; 

 geography of, 318; in time scale, 315 



Eohippus, 324, 325; skull of, 326; tooth 

 of, 326 



Eosin eye color in Drosophila, 344, 361 



Ephemerida, classified, 270 



Ephydatia, 170 



Epicrium ghitinosum, gills of, 122 



Epidermis, 14 



Epistylis, 31, 87 



Epistylis flavicans, 87 



Epithelial tissues, 108; examples of, 109; 

 functions of, 109 



Epithelium, ciliated, 63; germinal, 116; 

 nerve endings of, 163; occurrence 

 and function of, 108; olfactory, 164; 

 types of, 109, 110 



Epizoanthus americanus, a symbiote, 279 



Equation division, 211 



Equatorial cleavage, 217, 218 



Equatorial plate, 73, 74, 78, 81 



Equilibrium, 163 



Equus, 324, 325, 328 



Erepsin, 146 



Erosion, affecting fossils, 314 



Erythrodextrin, 143 



Eskimos, 336 



Esophageal commissure, 140 



Esophagus, 63, 117, 140, 229; of earth- 

 worm, 119 



Essay on Population (Malthus) 341, 342 



Ether, 187 



Ethusa, sperm of, 216 



Eudorina, 87, 88, 90, 93; reproduction of, 

 190 



Eiidorina elegans, 88, 89, 176, 177 



Euglena, 64, 85; flagellum of, 155 



Euglypha, 78, 81 



Eulamellibranchia, classified, 269 



Eupagurus pubescens, a symbiote, 279 



Euphausiacea, classified, 270 



Euplexoptera, classified, 270 



Eurypterida, classified, 270 



Eustachian tube, 226, 227, 231 



Eutheria, classified, 271, 274 



Euthyneura, classified, 269 



Evagination, 224 



Evidence, of evolution, 343; paleonto- 

 logical, 337 



Evolution. 5, 6, 18, 20, 21, 22, 23, 28, 256, 

 339-363, 347; artificial, 363; of 

 camel, 328-330; causes of, 354-357; 

 of the cephalopods, 330-331; course 

 of, 357-362; direction of, 360; of the 

 elephants, 319-324; environment 

 and, 359; evidence of, 343; a factor 

 in distribution, 299, 307; factors di- 

 recting course of, 358; genetics and, 

 257; of horse, 324-328; by hybridi- 

 zation, 362; inferential evidence of, 

 354; influence on taxonomy, 266; 

 lines of, 319 



Evolution theory, Charles Darwin and 

 the, 339 



Evolve, 339 



Excavations, revealing fossils, 314 



Ex-conjugant, 179 



Excretion, 58, 150-152 



Excretions, 58 



Excretory system, 114, 125-127 



Existence, struggle for, 341, 359, 360 



Experimental breeding in taxonomy, 267 



Experimental method, 11, 12 



Experiments on spontaneous generation, 

 166 



External gills, 233 



Extinct animals, as evidence of evolu- 

 tion, 351; migration of, 316, 317 



Extinction, 331; a factor in distribution, 

 306 



Eye, contraction of pupil, 161; develop- 

 ment of, 230; sensory cells of, 164 



Eyeless Drosophila, 345 



Fi, 243 



F2, 244, 249, 250 



F3, 245, 246 



F4, 246 



Factor, 240 



Factors directing course of evolution, 358 



Falconiformes, classified, 271 



Families, range of, 290, 291 



Family, defined, 263, 264; formation of 



name of, 265 

 Fasciola hepatica, 182, 183 

 Fat bodies, 120, 132, 147 

 Fats, 40, 52, 53, 54, 214; absorption of, 



146, 147; assimilation of, 146; di- 



