THE WAYS OF LIFE 191 



seen about an animal has to do with one or the other of 

 these pursuits'. 



Thus we see animals seeking for food, storing it, making 

 shelters and homes, adjusting themselves to the inanimate 

 world, e.g. in migration and concealment ; adjusting them- 

 selves to other creatures, e.g. in combat and flight ; seeking 

 and finding mates, preparing for the young, feeding and 

 otherwise caring for the young, and so on. There may 

 also be play during the early part of hfe, courtship at 

 adolescence, division of labour within a community, and 

 co-operation in societary enterprises, such as building a 

 dam or going on a slave-making raid. 



Behaviour of the Lower Animals : — Tropisms and 



MORE THAN TrOPISMS 



Tropisms. — In the lower animals, according to Loeb, 

 Bohn, and others, we must recognize the general occurrence 

 of ' tropisms ' and allied reactions. Every one knows 

 that plants growiag in a window bend towards the Hght, 

 and this is said to come about automatically, simply 

 because the side away from the hght grows more quickly. 

 We do not need to suppose that the plant longs for the 

 Ught. In the same way animals may move towards the 

 hght without ' wilhng ' to do so. Prof. Jacques Loeb 

 has explained what happens. When the hght comes from 

 one direction and strikes one eye, it sets up chemical pro- 

 cesses in one eye which are different (e.g. quicker) than those 

 in the other. But this affects the nerves and muscles of 

 the illumined side and the creature moves towards the 

 hght. For it is usually a bilaterally symmetrical animal, and 



