l6 FROM FISH TO PHILOSOPHER 



ting the desired combination. But suppose that every 

 time you draw a c, an a, or a ^ in a wrong combination, 

 you put these desirable letters back into the barrel and 

 discard only the undesirable letters. Your success is now 

 assured, because in time there will be only cs, as and 

 t's in the barrel; and, indeed, because of their rapid ac- 

 cumulation, you will probably succeed in drawing cat 

 in one set of three letters long before the barrel becomes 

 a pure pool of these three letters. Suppose, moreover, 

 that in addition to returning the cs, a's and t's to the bar- 

 rel (discarding all other letters), you clip together and 

 return any two desirable letters when they happen to be 

 drawn at the same time; you will then accumulate the 

 combinations ca, ct, and at at a rapid rate while you still 

 have a large number of t's, a's and cs needed to com- 

 plete the combination on a single drawing. Obtaining cat 

 now becomes a matter of such high probability that you 

 will succeed long before all the letters in the barrel have 

 been drawn once. Moreover, from the letters given at 

 the start you will have created the word cat which did 

 not exist in the barrel at the beginning. Simpson's al- 

 phabet is illustrated in principle, but by a different 

 graphic analogy, in Figure 3. 



Add to the reshuffling of 'stable* genes in sexual re- 

 production the facts that, so far as is known, every gene 

 can itself undergo mutation to produce a new gene with 

 markedly different effects on the body (and frequently 

 with profound effects on the action of other genes ) , and 

 that useful mutations and useful combinations tend to 

 be preserved and 'clipped together' by natural selection, 

 and thus to be returned to the 'barrel' where they supply 

 new combinations for variation and selection to work 

 upon, and it can be seen why evolution is a 'creative' 

 process, working frequently, ff not constantly, toward 

 more and more elaborate adaptation. Add the succession 

 of day and night, of summer and winter, add the great 

 cycles in the climate of the sea and earth that have 

 marked the geologic past, and one sees the process of 



