THE UNIQUENESS OF THE INDIVIDUAL 



assembly of populations is now subjected to training by peni- 

 cillin, and it is found that each individual member becomes 

 progressively adapted to resist its action. In a world in which 

 such populations were the analytical units, such a transforma- 

 tion would be called ''Lamarckian'' in whatever sense the scheme 

 illustrated by Fig. 5 may be so described. But within each 

 population, the adaptive change might very well be of the type 

 illustrated in its simplest form by Fig. 4. 



This reflection is instructive if we return to consider the 

 activities that may be supposed to accompany the transforma- 

 tion of an individual bacterial cell. It may be assumed that 

 there are alternative pathways of metabolism within each cell, 

 i.e. alternative enzyme sequences or metabolic gearings, as 

 there are, for example, alternative pathways for the degrada- 

 tion of glucose. Such metabolic pathways may for a variety of 

 reasons be so adjusted as to be mutually inhibitory, so that 

 only one prevails in any one of a possible set of steady states. 

 The inhibition of one such system therefore entails its replace- 

 ment by another. In other words, as Hinshelwood (1946) has 

 made clear, the Lamarckian transformation illustrated by 

 Fig. 5 may be Darwinian at the lower analytical level repre- 

 sented by the enzymic population or complex of intersecting 

 metabolic pathways wuthin the individual bacterial cell. Such 

 a description would be pointless for any except explanatory 

 purposes, but it shows that no discussion of the rival inter- 

 pretative powers of Darwinism and Lamarckism can have any 

 useful outcome unless a certain analytical level is defined and 

 adhered to. Hereafter we shall be concerned with individual 

 organisms as analytical units, for it is only in this context that 

 the rivalry is of any moment. 



The case for and against Lamarckism may be set out for 

 analysis in a variety of ways. Guided by the reflections of 

 Baldwin and Lloyd Morgan, I shall present it first in what 

 philosophers would call a '"weak"' or general form, and then in a 



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