Xii CONTENTS. 



CHAPTER IX. 



THE ETIDETsCE FROM SECONDARY SEXUAL CHARACTERS CON- 

 TINUED. — THE CAUSE OF THE EXCESSIVE MODIFICATION OF 

 MALE CHARACTERS. 



Tlie explanation of Daines Barrington and Wallace — "Reasons 

 for considering it inadequate — Darwin's explanation — 

 History of domesticated races shows that this does not go 

 to the root of the matter — The view that the male is more 

 exposed than the female to the action of selection — A 

 more fundamental explanation is needed — This is fur- 

 nished by our theory of heredity — Special difficulties — 

 Summary 207 



CHAPTER X. 



THE EVIDENCE FROM THE INTELLECTUAL DIFFERENCES BE- 

 TWEEN MEN AND ■v\^o:men 243 



CHAPTER XI. 



the theory of HEREDITY CONSIDERED AS SUPPLEZklENTARY TO 

 THE THEORY OF NATURAL SELECTION. 



Darwin believes that variations are purely fortuitous — Natural 

 selection cannot give rise to permanent race modifications 

 unless man}' individuals vary in nearlj-^ the same way, at 

 about the same time — The chances against this are very 

 great if variations are fortuitous — Argument from North 

 British Review — Darwin acknowledges the great weight 

 of this objection — It is removed bj' the theory of heredity 

 — The co-ordinated modification of complicated organs — 

 The time demanded by Darwin practically infinite — 

 ]\Iurphy's argument from the complexity of the eye — 

 Herbert Spencer's illustration — Our theory removes this 

 difficulty — Mr. Conn's objection — Saltatory evolution — 

 Evidence that it occurs — Spike horn buck — Ancon and 

 Mauchamp sheep — Black-shouldered peacock — The the- 

 ory of heredity accounts for saltatory evolution — Parallel 

 variation — Evidence of its occurrence — Evolution of the 

 medusae — General and special Homologies 275 



CHAPTER XII. 



RECAPITULATION AND CONCLUSION 313 



