Contents. 



Elimination and selection 



Modes of natural elimination illustrated 



Protective resemblance and mimicry 



Selection proper illustrated 



The effects of natural selection 



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 



Modes of adaptation : Progress 



Evolution and Kevolution 



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79 



80 



82 



93 



95 



99 



99 



108 



110 



112 



117 



119 



120 



CHAPTER V. 



HEREDITY AND THE ORIGIN OF VARIATIONS 



Heredity in the protozoa 



Eegeneration 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 



The inheritance or non-inheritance of acquired characters 



Origin of variations on the latter view 



Hypothesis of organic combination 



The extrusion of the second polar cell 



The protozoan origin of variations 



How can the body influence the germ ? 



Is there sufficient evidence that it does ? 



Summary and conclusion 



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 124 

 129 

 130 

 131 

 131 

 134 

 138 

 142 

 146 

 149 

 150 

 153 

 156 

 159 

 162 

 175 



CHAPTER VI. 



ORGANIC EVOLUTION. 



The diversity of animal life 



The evolution theory 



Natural selection : not to be used as a magic formula 



Panmixia and disuse 



Sexual selection or preferential mating 



Use and disuse 



The nature of variations 



The inheritance of variations 



The origin of variations 



Summary and conclusion 



. . 177 



181 



. . 183 



189 



..197 



209 



..216 



223 



. . 231 



241 



