SECTION D.— ZOOLOGY. 



ADAPTATION. 



ADDRESS BY 



Prof. D. M. S. WATSON, M.Sc, F.E.S. 



PRESIDENT OF THE SECTION. 



My predecessors in this chair in choosing the subjects of their addresses 

 have set no fashion which helps me to determine on what subject to talk 

 to you. Sometimes they have chosen to expound the details of that 

 particular field of zoology in which they have themselves worked, sometimes 

 they have discussed broad questions involving the fundamental assump- 

 tions of zoologists or speculated as to the beginnings of structures or of a 

 phylmn. When the section did me the honour to appoint me to this 

 position I was naturally tempted to devote an hour to the discussion of 

 those early reptiles which come from the Karroo system, animals which 

 lie near to the base not only of the mammals but of all the important 

 developments of the great class of reptiles. 



But on consideration I decided to make use of my opportunity to 

 discuss the significance of adaptation in animals. 



The only great generalisation which has so far come from zoological 

 studies is that of Evolution — the conception that the whole variety of 

 animal life, and the system of interrelationships which exists between 

 animals and their environment, both living and non-living, have arisen 

 by gradual change from simpler or, at any rate, different conditions. 



Evolution itself is accepted by zoologists not because it has been ob- 

 served to occur or is supported by logically coherent arguments, but 

 because it does fit all the facts of Taxonomy, of Palaeontology, and of 

 Geographical Distribution, and because no alternative explanation is 

 credible. 



But whilst the fact of evolution is accepted by every biologist the mode 

 in which it has occurred and the mechanism by which it has been brought 

 about are still disputable. 



The only two ' theories of Evolutioii ' which have gained any general 

 currency, those of Lamark and of Darwin, rest on a most insecure basis; 

 the validity of the assumptions on which they rest has seldom been seriously 

 examined, and they do not interest most of the younger zoologists. It 

 is because I feel that recent advances in zoology have made possible a 

 real investigation of these postulates that I am devoting my address to 

 them. 



