Contents. 



PAGE 



79 

 Elimination and selection . . ' 



Modes of natural elimination illustrated 



Protective resemblance and mimicry 



Selection proper illustrated .. 



The effects of natural selection .. "99 



Isolation or segregation 



Its modes, geographical, preferential and physiological 



Its effects .. 



Utility of specific characters 



Variations in the intensity of the struggle for existence . . 



Convergence of characters . . . . 117 



Modes of adaptation : Progress 

 Evolution and Revolution 



CHAPTER V. 



HEREDITY AND THE ORIGIN OF VABIATIONS. 



Heredity in the protozoa 



Regeneration of lost parts 



Sexual reproduction and heredity 



The problem of hen and egg 



Reproductive continuity 



Pangenesis 



Modified pangenesis 



Continuity of germ-plasm 



Cellular continuity with differentiation . . . . . . 142 



The inheritance or non-inheritance of acquired characters 



Origin of variations on the latter view 



Hypothesis of organic combination . . . . 150 



The extrusion of the second polar cell . . . . . . 1 53 



The protozoan origin of variations 



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 



