40 THE SOCIAL LIFE OF ANIMALS 



until perhaps a tenth of their number could be 

 found later in the season; with the autumn lushness 

 they increased again, only to fall back to some half- 

 million or so per acre during the winter cold. 



Similar communities exist among aquatic forms. 

 In fact one of the first demonstrations of such a 

 community was made for the animals living in and 

 on an oyster-bank. (82) A beautiful and penetrating 

 description of the interrelations that may be found 

 in a small lake was published not long after by the 

 late Professor Forbes (48) of the Illinois Biological 

 Survey, in which he pointed out that minnows com- 

 peted with bladderwort plants for key-industry or- 

 ganisms; and showed that when a black bass is 

 hooked and taken from the water the triumphant 

 fisherman is breaking, unsensed by him, myriads of 

 meshes which have bound the fish to all of the dif- 

 ferent forms of lake life. 



The existence of these communities is now gen- 

 erally recognized, and in order that they may exist 

 it seems that there must be a far-reaching, even if 

 vague and wholly unconscious, co-operation among 

 all the living creatures of the community. It is to 

 such relationships that Wheeler referred when he 

 said, "Even the so-called solitary species are neces- 

 sarily more or less co-operative members of groups 

 or associations of animals of different species." 



