THE CRITERIA OF LIVINGNESS 97 



§ 5. Effective Behaviour, Registration of Experience, 



and Vanability, 



So far we have sought to arrange in a logical way certain 

 insigTiia of organisms. Absolutely fundamental is the power 

 of persistent individuality in spite of ceaseless change. 

 There is a unifying idea of persistence or of functional 

 inertia. This led us to consider growth, multiplication, and 

 cyclical development. Here, perhaps, there is a unifying 

 idea of accumulating potentialities. We have now to recog- 

 nise that living creatures are characterised by effective be- 

 haviour, registration of experience, and variability. The 

 common note in this triad of qualities may not be obvious, 

 but is it not agency, self-expression, creativeness ? 



(a) Life is a kind of activity which comes to its own in ef- 

 fective behaviour, that is to say, in an organically determined 

 correlated series of acts which converge towards a definite re- 

 sult. Behaviour is seen at many levels and in diverse modes, 

 which will be discussed later, but its common features are 

 correlation, concatenation, individuality, and purposiveness. 

 Big words, indeed, for the Amoeba gliding along on the mud 

 of the duck-pond. And yet, if we take this Amoeba, and 

 lay aside the contempt which superficial familiarity breeds, 

 we find that we are only beginning to make its acquaintance. 



Professor Jennings describes a large Amoeba, a, which had 

 imperfectly swallowed a smaller one, h. The prisoner moved 

 as if trying to escape, the swallower moved as if trying to 

 prevent it. Finally the small one did get completely out 

 again, whereupon the large Amoeba, a, reversed its course, 

 overtook h, engulfed it completely, and started away. The 

 small Amoeba, again imprisoned, lay still until through the 

 movements of a there happened to be but a thin layer of 



