xiv CONTENTS 



PAGE 



74. On the Nature of the Developmental Process . . . 207 



(a) The Morphology of the Nucleus ; (b) " Morganism, " the 

 genes. 



75. On the Developmental Organization . . . .211 



76. On the Psycho-biological Conception of the Developmental 



Process . . . . . . . . .218 



(a) Development Hypotheses and Practical Researches. 



CHAPTER VH. HEREDITY 



77. On the Categories of Animals ..... 223 



(a) Species. 



78. On Hereditary Resemblances ...... 224 



79. On Hybridity ........ 226 



(a) Immediate and Ultimate Sterility ; {b) The Sign of the 

 Crossing. 



80. On Mendelian Hybridity ....... 228 



81. On the Cytological Phenomena associated with Mendelian 



Hybridity ....... 230 



(a) The Maturation of the Germ-cells ; (h) The Gametes ; 

 (c) " Crossing-over " of the Chromosomes ; (d) The Genes. 



82. On the Essentials of Mendelism ..... 237 



83. On Heredity in General . . . . . .238 



(a) The " Transmission of Characters " ; (6) Soma and Germ. 



CHAPTER VIII. TRANSFORM ISM 



84. On Categories of Organisms ...... 242 



(a) Organic Variability in General ; (b) The Analysis of Crude 

 Variability ; (c) Categories within the Local Race. 



85. On the " Causes " of Mutations . . ... . 249 



(a) The Multiple Values of a Characteristic ; (b) Organic 

 Fluctuations and the Environment ; (c) Mutations regarded as 

 very Improbable Fluctuations. 



86. On Hypotheses of Transformism : I. Natural Selection . 253 



(a) Origins of Wild Races not Similar to those of Domesticated 

 Races ; (b) Mendelism not an Explanation of Natural Trans- 

 formism ; (c) The hypothesis of Natural Selection. 



87. On Hypotheses of Transformism : II. Neo-Lamarckism . 259 



(a) Acquirements ; (b) Transformism by Acquirement ; (c) 

 The Evidence for Lamarckism. 



CHAPTER IX. THE EVOLUTIONARY CAREER 



/. Evolution in General 



88. On Evolution and Probability ..... 270 



89. On the Tendency in Cosmic Evolution . . . .271 



(a) Planetary Evolution ; (b) Chemical Evolution. 



90. On the Tendency in Organic Evolution .... 274 



