49 



Youth, maturity, and senescence of species, Hyatt. 



Germinal selection, Weismann. 

 General Conclusions. 



The prime factors in organic evolution are Variation 

 and the Struggle for Existence with the resulting 

 Natural Selection. 



Other important factors are Sexual Selection, Segre- 

 gation, Panmixia, and the Reversal of Selection. 



Supposed effects of the inheritance of acquired char- 

 acters and of constitutional tendencies improbable. 



The doctrine of evolution well founded in fact and es- 

 tablished in theory. 



IX. DEDUCTIONS FROM THE THEORY OF 



EVOLUTION. 



Ontogeny and phylogeny. 



Significance of Sex. 



Origin of death. 



Color. 



Relations of animals and plants. 



Social evolution. 



Philosopical results. 



" There are more things in heaven and earthy Horatio, 

 Than are dreamt of in your philosophy.^'' 



