GENERAL CONSIDERATIONS 357 



theory of Bethe, who thinks that we have not the right to 

 admit either sensations, perceptions or memories in ani- 

 mals. He refuses to allow animals any psychic qualities 

 whatever, and considers the presence of consciousness, 

 even in animals that can learn by experience, as a highly 

 problematic and improper assumption. The other theory 

 is the tropism theory of Loeb. However well Loeb's theory 

 may apply to certain organisms in the plant or animal 

 world, his mechanical interpretation is nil, in so far as the 

 movements of wasps are concerned, when he says i 1 "The 

 tropisms are identical for animals and plants. The expla- 

 nation of them depends first upon the specific irritability 

 of certain elements of the body surface, and second upon 

 the relation of symmetry of the body. Symmetrical ele- 

 ments at the surface of the body have the same irritability, 

 unsymmetrical elements have a different irritability. Those 

 nearer the oral pole possess an irritability greater than that 

 of those near the aboral pole. These circumstances force 

 an animal to orient itself in such a way that symmetrical 

 points on the surface of the body are stimulated equally. 

 In this way the animals are led without will of their own, 

 either toward the source of stimulus or away from it. Thus 

 there remains nothing for the ganglion cells to do but to 

 conduct the stimulus, and this may be accomplished by pro- 

 toplasm in any form." 



The theories of Loeb 2 and Bethe make not a beginning of 

 an explanation of the activities in Waspdom. Had either 

 of the gentlemen spent some time in the field with these 

 creatures, his mechanical theory, if formulated at all, would 



1 Holmes, Evolution of Animal Intelligence, p. 20. 1911. 



2 It must be remembered, however, that Loeb does not claim that all 

 the reactions of animals are tropisms. He recognizes three types of 

 behavior: tropisms, differential sensibility and associative memory. 

 He even states that he thinks he must admit that ants, wasps and bees 

 have associative memory. 



