2 ANIMAL LIFE AND SOCIAL GROWTH 



animals and plants live in associations, herds, 

 colonies or societies and even the so-called *soli- 

 tary' species are necessarily more or less co-opera- 

 tive members of groups or associations of individ- 

 uals of different species. Living beings not only 

 struggle and compete with one another for food, 

 mates and safety, but they also work together 

 to insure to one another these same indispensable 

 conditions for development and survival." 



Such descriptions of animal communities suggest 

 that in their organization they resemble individual 

 animals. Obviously there is no close resemblance 

 between these more or less loosely knit animal 

 communities and such a well organized animal 

 as a bee or a dog or a man, but all animals are 

 not so closely under the control of their central 

 nervous systems. With sponges and other lower 

 animals it is difficult to determine how much of 

 the living tissue belongs to one individual and how 

 much to another. Even in fairly well organized 

 animals such as starfishes, the different parts of 

 the body may work in decided opposition to each 

 other rather than in co-operation. When a star- 

 fish is placed on its back, three of the arms may be 

 working vigorously to turn in one direction and 

 be actively opposed by the other two, or the arms 

 may be attempting to right the animal by working 

 in three or even in five directions at the same time. 



