l8 FROM FISH TO PHILOSOPHER 



developed in various types of animals is almost in- 

 credible: it seems nearly impossible to think of a prac- 

 tical photoreceptor that has not appeared in one group 

 of animals or another, ranging from the diffuse sensitivity 

 of unspecialized cells to the elaboration of many differ- 

 ent types of compound eyes, and to the simple eye of 

 man— which is not necessarily the best. Again, apart from 

 the insects, wings have been developed three times 

 from the forelimbs of the quadrupeds— in the reptilian 

 pterodactyls, in the birds, and in the mammalian bats— 

 in each instance representing a different structural ex- 

 periment and a different solution. 



Progress can take a variety of forms, but it is only in 

 the development of increased physiological independ- 

 ence of environment, which, for mobile forms, involves 

 increased awareness and perception of the environment 

 and increased abihty to react accordingly, that we can 

 speak of evolution as being upwards rather than just 

 sideways. All evolution is adaptive, if by evolution one 

 refers only to those forms that survive beyond the time 

 and circumstance of their origin; and all evolutionary 

 adaptation is 'preadaptation' (though students of evolu- 

 tion use this word in a more specialized sense), since 

 the mutation must come first and the mutant organism 

 must then get along as best it can. Natural variation is 

 not adaptive— selection cuts off many more mutants than 

 by its grace are permitted to survive. It is natural selec- 

 tion that turns the randomness of natural variation into 

 an organically useful plan. 



When Linnaeus ( 1707-1778) , in his Systema Naturae 

 and other works, catalogued the plant and animal king- 

 doms into phyla, classes, orders, famihes, genera, and 

 species, he grouped them (even as Adam did when he 

 first named the animals) according to those obvious 

 anatomical affinities with which (so it seemed to him in 

 pre- evolutionary days) they had been endowed by the 

 act of Original Creation. But Darwin and all subsequent 

 evolutionists have seen in these biological relationships 



