CONTENTS 



CHARTER I 



PAGE 



The structure of living matter Unicellular and multicellular animals and 

 plants Life cycles of unicellular animals Reproduction in multi- 

 cellular animals and plants The life cycles of multicellular organisms 

 Theories of emboitement, pangenesis, and idioplasm Experiments 

 bearing u] 101 1 these ; theories ........ 1 



CHAPTER II 



Structure of a cell Phenomenon of cell division Selective division of 

 certain parts Theory identifying Niigeli's idioplasm with chromatin 

 Objections The maturation of the gametes The meiotic phase 

 The impossibility of particular characters common to the race being 

 borne by part ieulur eliromosoines Fertilisation Parthenogenesis 

 Fertilisation in unicellular animals Experiments in artificial fertilisa- 

 tion and their hearing upon the existence of an hereditary substance 

 Conclusions .13 



CHAPTER III 



Differentiation of cells Inborn and acquired characters Mental char- 

 acters in in. i n Physical characters Instinct Lamarck's theory The 

 Dai win-Wallace theory Weismann's theory Oscar Hertwig's theory 45 



CHAPTER IV 



Variation De Vries' mutation theory The case of (Enothera The dis- 

 appearance of characters Variation in grafts The cell layers in the 

 embryo Variations in Avild and domesticated races Arguments 

 against the origin of species per saltum Fertility of hybrids . . 59 



CHAPTER V 



Adaptation Difficulty of explaining by the mutation theory Examples 

 of adaptation Protective coloration Seasonal changes Imitative 

 adaptation Pitcher-plants Drosera The Yucca and the moth Pro- 

 nuba Parasitic adaptation The material provided by variation for 

 natural selection to work upon The biometrical principle Conclusions 77 



CHAPTER VI 



Racial and individual inborn characters Immunity to diseases Malaria 



Measles Tuberculosis Conclusions . . . . . . .102 



xi 



