INDEX 



479 



Senescence, individual: occurrence of, 

 in organisms, 2, 178, 461; significance 

 of, 3; definition of, 58, 185; general 

 character of, 63, 441; morphological 

 changes during, 86, 284; as condition 

 of rejuvenescence, 133, 186, 259, 461; 

 in protozoa, 142, 379; in relation to 

 endomixis, 143; in relation to hydranth 

 and medusa buds in Pennaria, 151, 256; 

 inhibition of, 167, 239, 257, 279,^303; 

 in relation to character of nutrition, 

 169, 276; theories of, 182, chap, xvi; 

 changes in water content during, 184, 

 279, 283; in relation to other periodi- 

 cities, 187, 192, 296; in vegetative life 

 of plants, 239; in whole and parts of 

 plants, 239, 241, 243; in growing tips 

 of plants, 244; in relation to spore 

 formation in plants, 251, 253; as con- 

 dition of specialized agamic reproduc- 

 tion in animals, 256; in absence of 

 growth, 282; changes in chemical con- 

 stitution during, 283; atrophy in later 

 stages of, 287, 301 ; internal determina- 

 tion of rate of, in warm-blooded ani- 

 mals, 303; in development of gametes, 

 349; in relation to maturation, 355; 

 in relation to gamete formation in 

 algae and fungi, 364; in relation to 

 gamete formation in mosses and ferns, 

 366; in relation to flowering, 368; 

 as condition of conjugation, 378; in 

 different races of Paramecium, $?>2; 

 in relation to gamete formation in 

 hydra, 384; in relation to gamete 

 formation in margelid medusa, 384; 

 in relation to gamete formation in 

 planarians, 384; in relation to gamete 

 formation in other invertebrates, 387; 

 in relation to gamete formation in 

 vertebrates, 388; in relation to par- 

 thenogenesis and zygogenesis in inver- 

 tebrates, 391, 392; in larval life cycle 

 of digenetic trematodes, 396; suscepti- 

 bility in early development in relation 

 to, 412; larval stages and metamor- 

 phosis in relation to, 420; as a wearing 

 out, 433; as an adaptation, 433; as 

 result of reproduction, 433; as result 

 of atrophy of sex organs, 434; as 

 result of inhibition of growth impulse, 

 434; as an intoxication, 434; as result 

 of organic constitution, 436; in relation 

 to surface and volume, 43 7 ; as result of 

 starvation of cells, 437; nucleoplasmic 

 relation in, 439; in relation to cyto- 

 morphosis, 440; as result of differentia- 

 tion, 442; as result of accumulation of 

 metaplasm, 443; in relation to decrease 

 of assimilatory capacity, 444; "dilu- 



tion" of nitrogen in plants during, 

 444, 453; as result of decrease in 

 nucleoplasmic interchange, 444; in 

 relation to colloid changes, 445; as 

 retardation of an autocatalytic reac- 

 tion by accumulation of products, 448; 

 not a special process, 459; in non- 

 living systems, 465. See also Age; 

 Age cycle; Development; Differentia- 

 tion; Senescence, evolutionary, racial. 



Senescence, racial: in protozoa, 136, 378; 

 in relation to endomixis, 143; in 

 Planar ia velata, 173, 179; in relation 

 to conjugation, 378, 383, 434; in 

 relation to parthenogenesis and zygo- 

 genesis in invertebrates, 390; in 

 potato, 426; conditions of, 426, 561. 



Senility: atrophy as characteristic of, 

 287, 301; morphological changes in, 

 287; as a "wearing out" of physiologi- 

 cal mechanism, 288, 433; mental, 297; 

 in relation to fatigue and exhaustion, 

 297; as result of atrophy of sex organs, 

 434; as result of special conditions not 

 connected with growth, 448. See also 

 Death; Differentiation; Senescence; 

 individual. 



Sida crystallina, oogenesis of, 343. 



Silphium, pollen grain and spermatozoid 



of, 334- 



Specification, 46. 



Spermatogenesis, in guinea-pig, 335. See 

 also Gamete formation; Gametes. 



Spermatogenous cell, segregation of, in 

 plants, 318, 320. See also Gamete 

 formation; Gametes. 



Spermatozoid of plants. See Gamete 

 formation; Gametes. 



Spermatozoon of animals. See Fertiliza- 

 tion; Gamete formation; Gametes. 



Spirogyra, gametic reproduction in, 316. 



Sporangium, 247, 250. 



Spore formation: in plants, 233, 238, 241, 

 247; in relation to senescence, 241, 

 248; rejuvenescence in, 252, 253; in 

 relation to age cycle in plants, 254; 

 in protozoa, 255. 



Sporophore, 248. 



Sporophyte: in relation to age cycle, 253; 

 in mosses and ferns, 253; origin of, in 

 apogamy, 322. 



Stability, physiological: nature of, 35, 39; 

 different degrees of, 41; in relation to 

 starvation, 44; increase in, during 

 development, 50, 183, 463; in relation 

 to metabolic rate, 51, 279; in relation 

 to evolution, 53, 194, 267,^ 298, 304, 

 460, 463; in relation to individuation, 

 227; increase in, during partial starva, 

 tion, 280, 282; of skeletal substance- 



