3IO THEORETICAL BIOLOGY 



the signal for the action to begin) the inner rhythm can set in, 

 to guide the animal confidently through the forest of indicators. 



In terms of human thought, the inner rhythm of the 

 animal knows the laws of the outer world, although the 

 animal gets no information thereon through the indications 

 at its disposal. It is this knowledge possessed by the inner 

 rhythm that I have called the " wisdom " of organisms. Of 

 course, there is no question here of knowledge or wisdom 

 in the human sense, but of a " congruity " of the internal pro- 

 cesses of the animal with the laws of the external world. 



For the instinctive action in the widest sense (embracing 

 also the tide-change in the protoplasm) it is immaterial 

 whether the law of the external processes consists in a regular 

 alternation of day and night, of the seasons of the year, 

 or of ebb and flow, or whether it is expressed spatially, as in 

 the geographical formation of those portions of the globe 

 used in the migration of birds, or in the organisation of the 

 birch-leaf for the beetle, or in the anatomical disposition of the 

 nervous system of its prey in the case of the ichneumon-fly, 

 or in the chemical reactions of the human tissues in the case 

 of the malaria parasite. Everywhere we see an autogenous 

 rhythm at work, which, from the factors held together by 

 the external laws, constructs its own path, a path which 

 is the more securely laid the firmer the external connection 

 of the factors. 



Beside these remarkable facts, which I describe as " con- 

 gruity," the question as to whether the rhythm is given 

 permanently by a corresponding framework, or develops anew 

 as occasion requires, appears quite subordinate. To inquire 

 into the inner rhythm that brings about this harmony involves 

 a far harder problem than the quite secondary consideration 

 as to whether, in a given instance, we have to do with an 

 isolated or with a lasting influence on the framework. 



In the case of the complicated and prolonged actions 



