6z8 



THE A M ERICA X NA TURA LIS T. [Vol. XXXV 1 1 . 



The synchronous reflexes are such complex movements of multiple 

 phases as exhibit a rhythm ; the metachronous are chain reflexes 

 in which each step serves as a stimulus for the next, of these 

 the homometachronous are coordinated, the heterometachronous 

 uncoordinated. 



In his discussion of instinct the author states that only simple 



means something which is essentially an elementary nature quality; 

 such, for example, are light, motion, heat. The simple stimulus he 

 contrasts with the individualized stimulus, which is appropriate for a 

 certain specialized type of sense organ. In this discussion much 

 credit is given to Loeb for his analyses of instincts. 



Attempts are made to get at the meaning of the concepts of neural 

 centres, spontaneity, autonomy, etc. Driesch thinks that the present 

 tendency to do away with the concept of brain centre is as far from 

 being desirable as is the uncritical acceptance of the old notion of 



The chapters on directed movements (taxes), reflexes, instincts, 



real subject, Activity (Handlung). The analysis of reflexes does 



action, for in the latter there are characteristics which are not 

 found in the simpler forms of movement. The criteria of action 

 which Driesch presents are the "Individuality of Association " and 

 the "Historical Basis of Reaction." Volitional action differs from 



a matter of certain elements of stimulus and response in definite 

 and unchanging relation, but of practical unpredictability. Loeb 

 makes the great mistake of supposing that all movements of the 

 organism can be described in terms of the factors which are common 

 to reflexes. Now, in the opinion of Driesch this is impossible, since 

 in action there is "autonomy"; we therefore have to take into 



such cannot be material for the biologist it is necessary to objectify 

 this factor. For Driesch the objective element which enables one 

 to give a description of action is the " psychoid." 



The book well deserves the attention of biologists who are interested 

 in the relations of their science to chemistry, physics, and psychology. 

 The chances are that few will be able to agree with the work as a 

 whole, but this makes it all the more valuable. It is of interest to 



