406 



SUBJECT INDEX. 



Daylight, effect of, on plants, 

 246; on flounder, 251 



Death, ages at, in man, 347 



Death rate, selective, in crabs, 

 338; in sparrows, 341 



Definite variations, 371 



Degeneration, explained by 

 germinal selection, 396 



Desert plants, 263 



Destruction, selective, in crabs, 

 337; in sparrows, 341; in mice, 

 351 



Determinants, 102; affected by 

 temperature, 236; necessity of 

 existence of, 358; and germinal 

 selection, 395 



Determinate variations, 373 



Development, of Echinoderm 

 larvae, effect of temperature on, 

 190, 194; rate of, in man, 201; 

 diminution of variability with, 

 204, 206; stages of, in relation 

 to reaction to environment, 

 190 



Digits, variation in, 56 



Dimorphism, in earwig, 38; in 

 crab, 39; in fish, 42, in marsh 

 plant, 42; origin of, 64, 65.; 

 seasonal, in Lepidoptera, 233, 

 239, 241, 242 



Diplogenesis, theory of, 357 



Discontinuous variations, origin 

 of, 51 ; importance of, in evolu- 

 tion, 52; as regard bud-varia- 

 tions, 187 



Disease, affects blonds more 

 than brunets, 93 



Diseases, affect identical twins 

 similarly, 116, 117, 118 



Disuse, effect of, on skull, 332; 

 on pigeon bones, 333; on duck 

 bones, 333; inheritance of ef- 

 fects of, 360 



Dogs, effect of Indian climate 

 on, 355 



Domestication, effect of, on vari- 

 ability, 221 ; on rabbit, 331 



Dominant characters in hy- 

 brids, 156, 159 



Dryness of soil, effect of, on 

 plants, 263 



Duck, effect of domestication 

 on, 333 



E 



Earwig, variation in forceps of, 

 37 



Echinoids, crosses among, 168; 

 specific metabolism of, 296, 

 298 



Echinoid larvae, effect of tem- 

 perature on size of, 229 



Elimination, of sparrows in 

 storm, 341; of gray mice, 350 



Embryos, rate of growth of hu- 

 man, 201; variability of, 206 



Environment, diminishing ef- 

 fect of, with development, 195; 

 variable reaction of organisms 

 to, 197; relation of, to develop- 

 ing plants, 199; effect of, de- 

 pendent on rate of growth, 203; 

 permanent effect of, 207; un- 

 favourable, as a cause of vari- 

 ability, 218; saline, as a direct 

 cause of variations, 277; may 

 produce local races, 310; action 

 of, through internal secretions, 

 358; may affect determinants 

 of germ-plasm, 366; does little 

 without natural selection, 392 



Environment, effect of, on 

 growth, 184, 194; on variabil- 

 ity of sparrow, 214; on varia- 

 bility of periwinkle, 216; on 

 variability, 218, 220; on repro- 

 ductive system, 221 ; on soma, 

 223; on colour of chrysalides, 

 258; on Lepidoptera, 316; on 

 plants, 311; on oyster, 314; 

 on snail, 314; on Porto Santo 

 rabbit, 331 



Epilepsy, inheritance of acquired, 

 364 



Equable Variability, Law of, 96 



Equipotency of parental herit- 

 ages, 150 



Error of Mean Square, 26 



Evolution, importance of varia- 

 tion in, 336; of aquatic plant, 

 393 



