xii Contents. 



Elimination and Mleetioa .. .. .. .. . . 7i 



Modes of naturul elimination illustrated 



Protective resemblance and mimicry . . . . . . 82 



s, I, ,-tiou proper illustrated .. .. .. .. .. 93 



The effects of natural selection . . . . . . . . 95 



Isolation or segregation . . . . . . . . . . 99 



Ita modes, geographical, preferential and physiological . . . . 91 



Itseffecta 108 



Utility of specific characters .. .. .. .. ..110 



Variations in the intensity of the struggle for existence . . 1 12 



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



Mo Jes of adaptation : Progress .. .. .. .. 119 



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 .. .. .. .. .. i::s 



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



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



Origin of variations on the latter view .. .. .. .. 14i> 



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 ? .. .. .. ..198 



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



Summary and conclusion . . . . . . . . 17f> 



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 . . . . . . . . . . I -: 



S, \iiul selection or preferential mating .. .. .. .. 1!>7 



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



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



The inheritance of variations . . . . . . . . 2'23 



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



Summary and conclusion .. .. .. .. ., -jn 



