BIOLOGICAL LECTURES. 



enough to outweigh possible instinctive opposition to the act, 

 or possible discomfort in its performance. Any one may dem- 



Nest 



FIG. 2. 



Nest 



FIG. 3. 



onstrate to himself the truth of this law over a wide range of 

 animal life by observing the nature of the acts selected and 

 of those eliminated by experience. He will find that the com- 



