Contents. 



Elimination and selection . . . . 79 



Modes of natural elimination illustrated 



Protective resemblance and mimicry . . . . 82 



Selection proper illustrated .. 



The effects of natural selection .. 



Isolation or segregation 



Its modes, geographical, preferential and physiological . . . 99 



Its effects .. .. .. .. .. .. .. 108 



Utility of specific characters 



Variations in the intensity of the struggle for existence . . 



Convergence of characters . . . . . . . . . . 117 



Modes of adaptation : Progress 



Evolution and Revolution 120 



CHAPTER V. 



HEREDITY AND THE ORIGIN OF VARIATIONS. 



Heredity in the protozoa . . . . . . . . . . 123 



Regeneration of lost parts . . . . . . . . 124 



Sexual reproduction and heredity . . . . . . . . 129 



The problem of hen and egg . . . . . . . . . . 130 



Reproductive continuity . . . . . . . . 131 



Pangenesis . . . . . . . . . . . . 131 



Modified pangenesis . . . . . . . . . . . . 134 



Continuity of germ-plasm . . . . . . . . . . 138 



Cellular continuity with differentiation . . . . . . . . 142 



The inheritance or non-inheritance of acquired characters . . 146 



Origin of variations on the latter view . . . . . . . . 149 



Hypothesis of organic combination . . . . . . . . 150 



The extrusion of the second polar cell .. .. .. ..153 



The protozoan origin of variations - . . . . . . . . 156 



How can the body influence the germ ? . . . . . . 159 



Is there sufficient evidence that it does ? . . . . . . 162 



Summary and conclusion . . . . . . . . . . 175 



CHAPTER VI. 



ORGANIC EVOLUTION. 



The diversity of animal life . . . . . . . . . . 177 



The evolution theory . . . . . . . . . . 181 



Natural selection : not to be used as a magic formula . . . . 183 



Panmixia and disuse . . . . . . . . . . 189 



Sexual selection or preferential mating . . . . . . . . 197 



Use and disuse . . . . . . . . . . . . 209 



The nature of variations. . . . . . . . . . . . 216 



The inheritance of variations . . . . . . . . 223 



The origin of variations . . . . . . . . . , . . 231 



Summary and conclusion . . . . . . . . . . 241 



