NOTES OX THE BEHAVIOR OF THE FIDDLE l< < K\U. 199 



activities than to reason about what they are and how to call 

 them. 



There is one striking property of very many reactions which 

 I would like to insist upon: their plasticity. In fact, the closer 

 we watch a fiddler the more obvious becomes the conclusion 

 that there is very little automatic in it. The practical mode of 

 accomplishing the various tasks depends on an infinity of minute 

 circumstances which are so various and different that surely 

 never two crabs work at their burrows under exactly the same 

 conditions. The animal performs its tasks in spite of the con- 

 dition being so various, and yet there is no doubt that every 

 single movement is largely depending on external stimuli. When 

 the pellet is carried out, the sand must be prevented from falling 

 back into the hole. And we see that in every single case the 

 sand is pushed, pulled and kneaded until it becomes properly 

 adjusted. Yet the properties of a pellet, as its size, its form, 

 the degree of moisture, the contents of organic matter and of 

 clay, the position towards the walls of the burrow, towards the 

 mouth of it, towards the other pellets, etc., are never the same. 

 All those properties bear very strongly on the actual movements 

 of the animal, which has to adjust not simply "a pellet of sand" 

 but always this single pellet with all its individual particularities. 

 The crab is always so careful about it that only rarely a few 

 grains roll back into the hole and it must estimate and judge 

 whether the work is done sufficiently well. Every single activity 

 connected with burrowing may be analyzed in the same way. 

 Choosing the spot where the burrow is to be made, grasping the 

 sand, carrying the pellet out, turning in the burrow so as to 

 make it circular, taking care of the burrow being conveniently 

 bent, conveniently oblique, of a definite length, avoiding the 

 obstacles, manufacturing the chamber, closing the burrow in 

 various manners, adapting the mode of acting to a situation 

 which is different in every successive second, each of those 

 activities again may be performed in infinitely different ways. 

 But they all bear on burrowing, which is only a small part of 

 the whole behavior of a fiddler crab. 



Given this unlimited variety of reactions, it becomes utterly 

 impossible to admit that each single reaction is referable to a 



