THE STRUGGLE F(>K UKK 



The more nauseous the caterpillars are to insect-eating 

 animals, the less likely are they to be molested. Thus, 

 Nature is herself making selections. The tendency of 

 this struggle and of this selection by nature is to re- 

 tain an equilibrium, a balance of forces.. Under con- 

 ditions that remain unchanged from year to year and 

 century to century, it is possible for species to adapt 

 their habits and instincts to their surroundings. But 

 under changing conditions, such as we know have taken 

 place in climatic conditions and in land and water 

 areas, species must adapt themselves, must become mod- 

 ified to these altered conditions, or cease to exist. The 

 tendencies of this selection brought about by the strug- 

 gle of life seem to be to bring to perfection all forms 

 engaged in the struggle. 



