4 CONTENTS 



CHAPTER III 



STRUGGLE FOR EXISTENCE 



Its bearing on natural bcIocUoii — The term used in a wide sense — Geo- 

 metrical ratio of increase — Rapid increase of naturalized animals and 

 plants — Nature of the chocks to increase — Competition universal — 

 Eflfects of climate — Protection from the number of individuals — Com- 

 plex relations of all animals and plants throughout nature — Struggle for 

 life most severe between individuals and varieties of the same species: 

 often severe between species of the same genus — The relation of organ- 

 ism to organism the most iniporlanl of all relations . . . .98 



CHAPTER IV 



NATURAL selection; OR THE SURVIVAL OF THE FITTEST 



Natural Selection: its power compared with man's selection; its power 

 on characters of trifling importance; its power at all ages and on 

 both sexes — Sexual Selection — On the generality of intercrosses be- 

 tween individuals of the same species — Circumstances favorable and 

 unfavorable to the results of Natural Selection ; namely, intercross- 

 ing, isolation, number of individuals — Slow a,ction — Extinction caused 

 by Natural Selection — Divergence of Character, related to the diversity 

 of inhabitants of any small area, and to naturalization — Action of 

 Natural Selection, through Divergence of Character, and Extinction, on 

 the descendants from a common parent — Explains the grouping of all 

 organic beings — Advance in organization — Low forms preserved — 

 Convergence of character — Indefinite multiplication of species — Sum- 

 mary 120 



CHAPTER y 



LAWS OF VARIATION 



Effects of changed conditions — Use and disuse, combined with natural 

 selection ; organs of flight and of vision — Acclimatization — Correlated 



