CONTEXTS IX 



CHAPTER X. 



Vitality. 



I. Isolation Cultures 469 



II. Organization and Differentiation 482 



1. Interdivi.sional Differentiations 483 



2. Cyclical Differentiations 488 



A. Cyclical Differentiations Peculiar to Youth 489 



B. Cyclical Differentiations Peculiar to Old Age 490 



C. Cyclical Differentiations Peculiar to Matiu-ity .... 494 



Sununary 505 



Special Bibliography 508 



CHAPTER XI. 



Phenomena Accompanying Fertiliz.\tion. 



I. The Environmental Conditions of Fertilization 509 



(a) Ancestry 509 



(b) Environment 510 



II. Internal Conditions at the Period of Fertilization 514 



III. The Process of Fertilization 516 



A. Meiotic Phenomena 518 



(a) Conjugant Meiosis 518 



(b) Gametic Meiosis (Wilson, 1925) 530 



(c) Zygotic Meiosis (Wilson) 531 



B. Disorganization and Reorganization 534 



(a) Phenomena of Disorganization 534 



(b) Metagamic Activities and Reorganization 535 



I^'. Parthenogenesis , . . 539 



A. Endomixis 540 



B. Autogamy 545 



Special Bibliogi-aphy 551 



CHAPTER XII. 



Effects of Reorganization and the Origin of Variations in the Protozoa. 



I. Effects of Reorganization on Vitality 552 



1. Renewal of Vitality as a Result of Conjugation 558 



2. Intensity of Vitalit\^ and Extent of Renewal 559 



3. Relative \'itality of Different Series and Effect of Parents' Age on 



^'itality of Offspring 563 



4. Rejuvenescence After Parthenogene.sis (Endomixis) ... 564 

 II. Heredity and Variations in Protozoa 566 



A. Uniparental Inheritance 567 



B. Biparental Inheritance .... 575 



Special Bibliography 583 



Bibliogi-aphy 585 



