22 THE SOCIAL LIFE OF ANIMALS 



reach another near-by isopod. When I used five or 

 ten individuals at a time, as I had done in the labo- 

 ratory, they piled together in small close clusters 

 that rolled over and over in the gentle current. 

 Only by testing them singly could I get away from 

 this group behavior and obtain a response to the 

 current; and even this reaction was disconcertingly 

 erratic. 



It took another year of hard work to get this con- 

 tradictory behavior even approximately untangled; 

 (i) * to find under what conditions the attraction of 

 the group is automatically more impelling than keep- 

 ing footing in the stream; and that was only the 

 beginning of the road that I have kept from that 

 April day to this time, continuing to be increasingly 

 absorbed in the problems of group behavior and 

 other mass reactions, not only of isopods, but of all 

 kinds of animals. 



As the years have gone on, aided by student and 

 other collaborators and by the work of independent 

 investigators, I have tried to explore experimentally 

 the implications of group actions of animals. And 

 necessarily, too, I have had to turn to the world's 

 literature to find what others have done and are 

 doing along this line. 



* Detailed citations to more complete statements will be found in 

 the bibliography. 



