CONTENTS 



PART I 



CRITIQUE OF THE ELEMENTALIST CONCEPTION OF THE 



ORGANISM 



B. The Production of Individuals by Other Indiridiuils (Concluded) 



CHAPTER PAGE 



XIV. EVIDENCE FROM METAZOAN GERM-CELLS THAT SUBSTANCES 



OTHER THAN CHROMATIN ARE THE PHYSICAL BASES OF 

 HEREDITY .......... 1 



Evidence from spermatozoa, 1. Spermatozoa subject to 

 heredity as well as "bearers of heredity," 1: (a) Illus- 

 trated by the ontogeny of mammalian sperm, 4; (k) Illus- 

 trated by the ontogeny of an insect sperm, 9. Evidence from 

 the ovum, 15: (a) eggs of ascidians the facts, 16; (6) 

 Conklin's interpretation, 19. Critical examination of Conk- 

 lin's interpretation, 23. 



XV. EVIDENCE FROM SOMATIC HISTOGENESIS IN THE MULTICELLULAR 



ORGANISMS 32 



The mitochondrial theory of heredity, 32. The mitochon- 

 dria! theory tested by the ontogeny of spermatozoa, 36. The 

 mitochondrial theory tested by histogenesis, 37. The un- 

 tenable hypothesis that cytoplasm of the ovum is inheritance 

 material for general but not for special characters, 40. Spe- 

 cies attributes in single cells of adult organisms, 43- The 

 spinules of the ascidian genus styela, 44- The spicules of 

 sponges and other invertebrates, 50. The '"hairs" of higher 

 plants, 55. Cell-wall structures in higher plants, 57. The 

 morphology of striated muscle fibers, 60. The physiology of 

 muscle fibers, 61. Summary of positive information about 

 the physical basis of heredity, 64. 



XVI. THE INHERITANCE MATERIALS OF GERM-CELLS INITIATORS 



RATHER THAN DETERMINERS ...... 66 



Antecedents of the cytoplasmic and nuclear theories of in- 



ix 



