INDEX 



477 



Pollen grain: development of, 320; 

 rate of oxidation in development of, 

 349, 374- 



Polyembryony: in armadillo, 231, 269; 

 in insects, 268. 



Preformation, 46. 



Primitive germ cell. See Germ path. 



Progression, 57. See also Development; 

 Differentiation; Senescence. 



Protamine, in sperm head, 353. 



Proteids: occurrence of, in organisms, 

 14; labile molecule of, 14, ig; dis- 

 tinction between living and dead, 15; 

 changes in, at death, 16; significance 

 of, for life, 20; molecular constitution 

 of, 20, 277; colloid character of, 20; 

 synthesis of, in growth, 39, 278; physio- 

 logical stability of, 39; nutrition 

 experiments with specific, 278; changes 

 in proportional amount of, during 

 senescence, 283, 444; in differentiation 

 of sperm head, 353. See also Colloids; 

 Stability, physiological; Substratum. 



Prothallium, 238, 245, 366. 



Protoplasm: chemical conception of, 14; 

 physico-chemical character of, 19; 

 undifferentiated, 48, 51, 245; changes 

 in aggregation of, 50; evolutionary 

 senescence of, 194, 464. See also 

 Colloids; Proteids; Substratum. 



Protozoa: agamic reproduction and 

 rejuvenescence in, 136; division in, 

 137; occurrence of death in, 305. See 

 also Infusoria. 



Radiate, 200. 



Reconstitution: in Planaria doroto- 

 cephala, 103; rejuvenescence in, 107, 

 no, 114, 116, 118, 180, 240; in rela- 

 tion to internal and external factors, 

 hi; degrees of, in; repeated, in 

 Planaria dorotocephala, 118; resem- 

 blance of, to agamic reproduction, 126, 

 132, 13s, 140; after partial involution 

 in Planaria velata, 172; termination of, 

 181; origin of axial gradient in, 207; 

 independence of apical region in, 210, 

 213; dominance and subordination in, 

 213, 215; of head in Planaria doroto- 

 cephala, 215; resemblance of, to embry- 

 onic development, 215; spatial factor 

 of dominance in, 222. 



Redifferentiation. See Dedifferentia- 

 tion; Development; Senescence, indi- 

 vidual. 



Reduction: definition of, 34, 37; chemical 

 conception of, 38; during starvation 

 in Planaria dorotocephala, 35, 44, 155; 

 during decreased metabolism, 45; after 

 fragmentation in Planaria velata, 131; 



of cell size in starvation, 155; 

 variable limit of, in Planaria doroto- 

 cephala, 156; rate of, in starvation in 

 Planaria dorotocephala, 162; of bran- 

 chial region in Clavellina, 258; of less 

 stable constituents during partial 

 starvation, 281; difference between, 

 and atrophy, 288; in fishes, 300. See 

 also Dedifferentiation; Rejuvenescence. 



Regeneration in excess, 43. 



Regression, 57, 155. See also Dediffer- 

 entiation; Reconstitution; Reduc- 

 tion; Rejuvenescence; Reproduction; 

 agamic, gametic. 



Rejuvenescence: occurrence of, in gen- 

 eral, 3, 4, s, 8, 64, 178, 180, chaps. X, 

 xii, XV ; definition of, 58; general char- 

 acter of, 64, 186; Maupas' conclusions 

 concerning, 64, 377, 434; in reconstitu- 

 tion in Planaria dorotocephala, 107; 

 in reconstitution in other forms, no; 

 degrees of, in reconstitution, 114, 180; 

 degrees of, in experimental and gametic 

 reproduction, 116; in repeated recon- 

 stitution, 118; in agamic reproduc- 

 tion in Planaria, 126; in agamic re- 

 production in infusoria, 141, 378; in 

 relation to endomixis, 143; in agamic 

 reproduction in hydra, 146; in agamic 

 reproduction in Pennaria, 149, 151; 

 in starvation in Planaria, 157, 178; 

 in relation to acclimation during starva- 

 tion, 165; in relation to character of 

 nutrition, 169; in relation to cell 

 division, 182, 242; in relation to 

 gametic reproduction, 186, 192, 270, 

 chap. XV, 434; . in relation to other 

 periodicities, 187, 296; Braun's ideas 

 concerning, 237; in vegetative life of 

 plants, 239; in plant cell, 24s; in spore, 

 252, 253; in agamic reproduction in 

 lower animals, 255; without reproduc- 

 tion in lower animals, 256; morpho- 

 logical evidence for, in animals, 257, 

 294; as result of senescence, 259; 

 limitation of, in higher animals, 267, 

 276; after hibernation, 296; in nervous 

 system, 297; after starvation in higher 

 animals and man, 298; after loss of 

 weight in disease, 299; during starva- 

 tion in fishes, 300; after starvation 

 in amphibia, 300; in transformation 

 of flower into vegetative shoot, 377; 

 in different races of Paramecium, 382; 

 in daphnid Crustacea, 392, 394; in 

 larval life history of digenetic trema- 

 todes, 396; evidence for occurrence 

 of, in embryonic development, 411, 

 412; period of developmental, in 

 Nereis and Arenicola, 416; degree and 



