262 EVOLUTION, GENETICS, AND EUGENICS 



of Darwinism at the hands of Professor V. L. Kellogg as it appears in 

 his book Darwinism To-Day. 



A much briefer and considerably more general defense is that of 

 J. L. Tayler, which is as follows. 



GENERAL DEFENSE OF DARWINISM^ 



J. L. TAYLER 



To realise how far the theory of selection is capable of explaining 

 the facts of organic evolution, it is necessary to bear in mind the 

 postulates in which the theory is founded. 



1. It is obvious that natural selection can only act by preserv- 

 ing or eliminating the complete organism. Selection must therefore 

 be organismal. This Darwin and other selectionists have clearly 

 recognised. 



2. As the whole organism must survive, if the favourable variation 

 or variations are to be preserved, it follows that certain minor un- 

 favourable variations may also be preserved if they happen to exist 

 in an individual which survives on account of its major favourable 

 variations. And since no individual is completely adapted to its 

 environment, it follows that there must be always a variable amount 

 of residual unfavourable variability in every organism. 



3. This residual unfavourable variability may be of considerable 

 utiUty under changed conditions. 



4. Complementary specialisation of parts, as Spencer has shown, 

 is favourable to successful competition, and as it is the whole organism 

 that is selected or eliminated, it follows that any weakness of one 

 specialised part, since it would disturb the balance of all, would be 

 detrimental. The more complex the organism, the more specialised 

 the structures, the more dependent one part will be on the others for 

 its existence, hence a complementary specialising tendency will be 

 favoured by selection, and therefore all struggles of one part of an 

 organism with another will be reduced to a minimum. 



It is clear that there must be some underlying criterion which 

 determines whether any given organism shall be selected or not, and 

 that criterion must be the net result of its adaptabiHty to its environ- 

 ment. One organism may conceivably survive, by its possession of 

 a large number of small favourable variations, while another may 

 survive in virtue of a single valuable one, but in each case it would be 



' From J. L. Tayler, "The Scope of Natural Selection," Natural Science, i8qq. 



