474 



SENESCENCE AND REJUVENESCENCE 



Infusoria: age changes in, 136; agamic 

 reproduction in, 137; endomixis in, 

 143; rhythms of growth and division 

 in, 143; immortality of, 145. 



Inhibition: in production of subnormal 

 forms in Planaria, 113; of senescence, 

 167, 239, 257, 27Q, 303. 



Integration, physiological, 224, 227, 

 267, 424, 460. See also Dominance; 

 Individuation; Isolation, physiologi- 

 cal; Reconstitution; Reproduction, 

 agamic, experimental. 



Intelligence: in construction of machine, 

 29; in organism, 30; in relation to 

 structure, 30. 



Involution in Planaria velata, 172. 



Irritability, Winterstein's conception of, 

 70. 



Isolation, physiological: m Planaria 

 dorotocephala, 124; in Planaria velata, 

 130; in Ttibularia, 220; in plants, 221, 

 239; as condition of reproduction, 229; 

 by increase in size, 229, 231, 239; 

 by decrease of dominance, 229, 231; 

 effect of, 230, 239; by decrease in con- 

 ductivity, 232; by direct action of 

 external factors, 232; infrequency 

 of, in higher animals, 268; in partheno- 

 genesis, 406; in segmentation of Nereis 

 larva, 422. See also Dominance; 

 Individual; Individuation. 



Katabolism: 14, 43> 278. 



Lability, 14, 17, 18, 19. 38- See also 



Stability, physiological; Substratum. 

 Larva: of trematodes, 395: of Nereis, 



414, 421; characteristics of, 420; 



metamorphosis of, 420; segmentation 



in, 421. 

 Lecithin: as autocatalyst of growth, 



454; reversal of development by, 454; 



disappearance of, in early development, 



454- 

 Life: neo-vitalistic conception of, 9; 

 chemical conception of, 15; physico- 

 chemical conception of , 19, 26; relation 

 to colloids, 22, 26; substratum and 

 reactions both necessary for, 26; be- 

 ginning of, 26; indissociability of 

 structure and function in, 28; relation 

 of intelligence to, 30, 31; Huxley's 

 conception of, 41; cyclical character 

 of, 59; temperature coefficient of 

 length of, 68, 308; without gametic 

 reproduction, 99, 130, 136, 239, 366 

 369, 386, 387, 3S8; length of, in higher 

 animals, 301; factors in length of, 302; 

 relation of length of, to time, 303; 

 theories of length of, 304- See also Age; 



Age cycle; Death; Dedifferentiation; 

 Differentiation; Life cycle; Rejuvenes- 

 cence; Senescence, individual, racial, 

 evolutionary. 



Life cycle: occurrence of, 59; in rela- 

 tion to age cycle, 182; of plants, 252, 

 254, 365, 369; of infusoria, 382;, of 

 daphnid Crustacea, 389; of rotifers, 

 392; of digenetic trematodes, 395. 

 See also Life. 



Limuhis polyphemits: in relation to evolu- 

 tionary senescence, 193; carbon-dioxide 

 production in nervous system of, 273. 



Lingula, in relation to evolutionary 

 senescence, 193. 



Lipoids: in membranes, 25; role of, in 

 narcotic action, 69, 75; increase of, in 

 animal oogenesis, 353. 



Lumbriculiis, rejuvenescence of, in recon- 

 stitution, no. 



Maintenance: difference between, and 

 growth, 278; energy requirement for, 

 in mammals, 306. 



Maturation: as a cause of death, 307, 

 309; in relation to life cycle in plants 

 and animals, 324; cytology of, 353; 

 heterotypic division in, 354; physio- 

 logical interpretation of, 355, 356; con- 

 ditions of, in animal egg, 355; in germ 

 cells of trematode larvae, 395; differ- 

 ent conditions of, in sea-urchin and 

 starfish, 405; increase of oxidation 

 during, 405, 406, 413; in partheno- 

 genic animal eggs, 407. 



Meganucleus: division of, 137; behavior 

 of, in endomixis, 143. 



Megaspore, of seed plants, 320. 



Meristematic tissue, 244, 246. 



Mesostomatidae, susceptibility of, in 

 relation to age, loi. 



Metabolic rate: in relation to age, 65, 

 178, 183, 186, 271; in relation to sus- 

 ceptibility, 66, 71, 72, 73. 79, 82; 

 susceptibility methods of comparing, 

 73, 77, 82; increase in, during recon- 

 stitution in Planaria dorotocephala, 

 106; increase in, during reconstitution 

 in various other forms, no; increase 

 in, in agamic reproduction in infusoria, 

 142; increase in, during starvation in 

 Planaria dorotocephala, 156; decrease 

 in, during loading of pancreas cell, 189; 

 in axial gradients, 202, 243; in biaxial 

 forms of Tiibularia, 211; in relation to 

 dominance, 216, 224; in relation to 

 position of parts, 222; in relation to 

 transmitted changes, 225; in relation 

 to degree of individuation, 228; in 

 relation to physiological isolation, 232; 



