412 



SUBJECT INDEX. 



Reaction of organisms to environ- 

 ment, variable, 197 



Recessive characters in hybrids, 

 156, 159 



Reciprocal crosses, 112 



Regression, in sweet-peas, 126; 

 in man, 127; coefficient of, 

 127, 128, 132; towards medi- 

 ocrity, 129; weeded out by 

 selection, 154; in Daphnia 

 magna, 178 



Relative Probable Error, an 

 index of variability, 20, 21 



Reproductive Selection, 87; in 

 sparrow, 214 



Reproductive system, correlation 

 with, 86; effect of, on internal 

 secretions, 94; effect of en- 

 vironment on, 221 



Resemblance, protective and 

 aggressive, 255 



Retardation of growth, persist- 

 ence of, 204, 207, 208 



Reversion, Law of, 133; in man, 

 139; in dog, 139; in calf, 140; 

 in pigeons, 140; in fowls, 142; 

 in mice, 142; produced by 

 crossing, 143; attempted ex- 

 planation of, 144; in Lepidop- 

 tera, 234, 239 



Ricin, acclimatisation to, 386 



Ripeness of sex-cells, variation 

 in, 110, 113 



Rock-pigeon, reversion to charac- 

 ters of, 140, 141 



Roots, interchange of, with 

 stems, 376 



Rothampstead experiments, 282 



S 



Saline solutions, acclimatisation 

 to, 382, 383, 384 



Salinity, effects of, on develop- 

 ment, 192, 199; on plants, 269; 

 on garden cress, 270; on frogs, 

 271; on worms, 271; on Arte- 

 mia, 271, 274; on common 

 cockle, 275; on Littorina, 278; 

 on Tubularia, 278; on sea- 

 urchin larvae, 279 



Sandwich Islands, snails of, 315 



Sciurus carolinensis, variation 

 of, 4 



Season, effect of, on size of 

 larvae, 109; on structure of 

 hybrids, 111 



Seasonal, variation in size of 

 larvae, 109; dimorphism in 

 Lepidoptera, 233, 239, 241, 

 242; forms, among Lepidop- 

 tera, produced by temperature, 

 236, 241, 242; adaptation, 234, 

 241, 243 



Sea-urchin larvae, relation of 

 growth of, to salinity, 279 



Sea-urchins, specific metabolism 

 of, 296, 298 



Secretions, internal, affect repro- 

 ductive system, 94; and en- 

 vironment, 358 



Seed capsules, effect of nutrition 

 on size of, 200 



Selection, effect of, on variability, 

 182; in sparrow, 213; effect of, 

 on breeding true to type, 153; 

 artificial, effect of, on vari- 

 ability, 211, 222; Genetic, 87; 

 Germinal, 395; Periodic, in 

 mollusc, 345; Physiological, 

 66 



Selection, Natural, effect of, on 

 variability, 211; action of, on 

 variations, 335; validity of, 

 336; in crab, 337; in sparrow, 

 341; in mollusc, 345; in man, 

 347; in mouse, 350 



Sex, effect of, on correlation, 82, 

 83; and prepotency, 151; 

 function of, in evolution, 180, 

 185 



Sex-cells, effect of nutrition on, 

 104; staleness of, 105 



Sheep, effect of feeding on, 294 ; 

 effect of conditions of life on, 

 354 



Shells, variability of, 206, 214; 

 of -cockle, affected by salinity, 

 275 



Shore plants, 269 



Shrimps, measurements of local 

 races of, 13 



