92 Presidential Address 



distribution of pigment cells, has come 

 about on merely mechanical principles. 

 It would be as easy to explain the sprout- 

 ing of the cantilevers of the Forth Bridge 

 from its piers, or the flocking of the stones 

 of the Nile Dam by chemiotaxis. Flowers 

 attract insects for fertilisation; and fruit 

 tempts birds to eat it in order to carry 

 seeds. But these explanations cannot 

 be final. We have still to explain the 

 insects. So much beauty cannot be 

 necessary merely to attract their atten- 

 tion. We have further to explain this 

 competitive striving towards life. Why 

 do things struggle to exist? Surely the 

 effort must have some significance, the 

 development some aim. We thus reach 

 the problem of Existence itself, and the 

 meaning of Evolution. 



The mechanism whereby existence en- 

 trenches itself is manifest, or at least has 

 been to a large extent discovered. Natur- 

 al Selection is a vera causa, so far as it goes; 

 but if so much beauty is necessary for in- 

 sects, what about the beauty of a land- 

 scape or of clouds? What utilitarian 



