LECTURE XXIV. 



N A T u R A i, SELECTION. 



Darwin's phrase synonymous with Spencer's term, 

 " Survival of the fittest," in the struggle for existence. 

 Fittest under the peculiar conditions. Nature no 

 respecter of persons. Not necessarily best or most 

 specialized. But so in long run ; through human 

 reaction. Illustration of a swimmer lost through help- 

 fulness. In long run he who brings sunshine and 

 freedom to others receives sunshine and freedom from 

 others. 



" With much the same result as that which the 

 farmer obtains by selecting his seed corn, the gardener 

 by thinning out his beds, or the cattle raiser by sell- 

 ing off his roughest calves for veal, Nature is at work on 

 an inconceivably great scale, thinning out the least 

 perfect individuals of each species." Bergen. 



Illustrations. Rabbits, grey, brown and white ; 

 weasels ; owls ; bears ; ptarmigans. Colors of fishes : 

 surface colors ; zone of olive green alga? ; zone of red 

 algae ; zone of inky darkness ; phosphorescent spots. 

 Birches of Norway. The Hrse series. Evolution of 

 lungs and swim-bladder. 



Mimicry ; use of insignificance. Recognition marks. 

 Division of labor. Sexual selection. Preference of 

 females for bright colors ; bright colors go with 

 strength. Questions unsettled. 



