362 lotka: efficiency in organic evolution 



Moreover, we shall not, on this occasion, discuss those properties 

 which relate to the birthrate.^ 



And again, of the properties which determine the deathrate, 

 we shall suppose the passive resistance of the type of organism 

 under consideration as given, and shall devote our attention solely 

 to the analysis of that mechanism or, to use a phrase that does 

 not invite fruitless controversy, that system, which constitutes 

 the individual's means of active opposition to unfavorable influ- 

 ences. We shall study the relation which the efficiency or pre- 

 cision of this mechanism or system bears to the fitness (gauged 

 by r) of a given type of organism. 



As regards this mechanism or system, it was pointed out in 

 the paper cited above, that all the actions of the organism form 

 part of a cycle, the so-called sensory-motor cycle, or, better, 

 receptor-effector cycle. 



For, every action is more or less directly conditioned by sense 

 impressions received by the organism. Between the mipression 

 or impressions received and the action or actions conditioned 

 thereby various steps may intervene. In the simplest case a 

 reflex action may be the direct and immediate result of a sense 

 impression. In other cases the action may lag far behind the 

 impression or impressions to which it is referable, and among 

 the intervening steps that lead from the impression to the action 

 may be certain phenomena which form objects of the individual's 

 consciousness, phenomena of wilP (desire, choice or selection) 

 and phenomena of mentation (logical deduction, etc.) 



The efficiency of the receptor-effector system, and hence the 



^ It is hoped to develop this phase of the subject at a later date along lines 

 which have been suggested by the method here laid down. 



5 It is not intended here to open up a discussion regarding the question ot free 

 will. All that is meant to be implied by the expression "selection" is that the 

 individual has a consciousness, a sensation or a belief of making use of a specific 

 faculty commonly denoted by the word will, in determining which of two or more 

 seemingly possible courses presented to him is to be followed. We are not here 

 concerned with the nature of this faculty of will, but only with the comparison, 

 as regards their fitness, of two or more types of organisms, alike in all other 

 respects, but differing in the particular manner in which they effect their selection; 

 that is to say, differing in the particular type of their will; or, in other words, 

 differing in their sense of 'value. 



