432 



EVOLUTION AND ANIMAL LIFE 



L 



feeding, those of self-defense and of strife, the instincts of play, 

 the climatic instincts, and environmental instincts, those which 

 direct the animal's mode of life. 



Altruistic instincts are those which relate to parenthood 



and those which are concerned 

 with the mass of individuals of 

 the same species. The latter 

 may be called the social instincts. 

 In the former class, with the in- 

 stincts of parenthood, may be in- 

 cluded the instincts of courtship, 

 reproduction, home-making, nest- 

 building, and care for the young. 



The instincts of feeding are 

 primitively simple, growing com- 

 plex through complex conditions. 

 The protozoan absorbs smaller 

 creatures which contain nutri- 

 ment. The sea anemone closes 

 its tentacles over its prey. The 

 barnacle waves its feet to bring 

 edible creatures within its mouth. 

 The fish seizes its prey by direct 

 motion. The higher vertebrates 

 in general do the same, but the 

 conditions of life modify this 

 simple action to a very great 

 degree. 



In general, animals decide by 

 reflex actions what is suitable 

 food, and by the same processes 

 they reject poisons or unsuitable 

 substances. The dog rejects an 

 apple, while the horse rejects a 

 piece of meat. Either will turn 

 away from the offered stone. Al- 

 most all animals reject poisons 



instantly. Those that fail in this regard in a state of nature 

 die and leave no descendants. The wild vetches or "loco- 

 weeds " of the arid regions affect the nerve centers of animals 

 and cause dizziness or death. The native ponies reject these 



FIG. 267. Part of branch of oak 

 tree, showing acorns placed in 

 holes in the bark by the Cali- 

 fornia woodpecker, Melanerpes 

 jormicivorus bairdii. (From 

 photograph taken at Stanford 

 University, California.) 



