HISTORICAL SPECULATIONS 13 



case. JVageli thought that there exists in hving ma- 

 terial an innate power to grow and expand. He 

 vehemently protested that he meant only a mechan- 

 ical j^rinciple but, as he failed to refer such a princi- 

 ple to any properties of matter known to physicists 

 and chemists, his view seems still a mvsterious affir- 

 mation as difficult to understand as the facts them- 

 selves which it purports to explain. 



Nageli compared the process of evolution to the 

 growth of a tree, whose ultimate twigs represent the 

 living world of species. Xatural selection plays only 

 the role of the gardener who prunes the tree into 

 this or that shape but who has himself lyroduced 

 nothing. As an imaginative figure of speech Xageli's 

 comparison of the tree might even today seem to 

 hold if we substituted propagation and variation for 

 "growth," but although we know so little about what 

 causes variation there is no reason for sujjposing it 

 to be due to an inner vague impulse. 



In his recent presidential address before the Brit- 

 ish Association, Bateson has inverted this idea. I 

 suspect that his effort was intended as little more 

 than a tour de force. He claims for it no more than 

 that it is a possible line of speculation. Perhaps he 

 thought the time had come to give a shock to our too 

 confident views concerning evolution. Be this as it 

 may, he has invented a striking paradox. Evolution 

 has taken place through the steady loss of inhibiting 



