BIOLOGICAL WRITINGS OF SAMUEL BUTLER 27 



Of the order of unconscious memory, latent till the arrival of 

 the appropriate stimulus, is all the co-operative growth and 

 work of the organism, including its development from the 

 reproductive cells. Concerning the modus operandi we know 

 nothing; the phenomena may be due, as Hering suggests, to 

 molecular vibrations, which must be at least as distinct from 

 ordinary physical disturbances as Rontgen's rays are from 

 ordinary light ; or it may be correlated, as we ourselves are 

 inclined to think, with complex chemical changes in an intricate 

 but orderly succession. For the present, at least, the problem 

 of heredity can only be elucidated by the light of mental, and 

 not material, processes." 



It will be seen that I express doubts as to the validity of 

 Bering's invocation of molecular vibrations as the mechanism 

 of memory, and suggest as an alternative cyclic chemical 

 changes. This view has recently been put forth in detail by 

 J. T. Cunningham in his essay on the " Hormone^ Theory of 

 Heredity," in the ArcJiiv fur Entivicklungsmechanik (1909); but 

 I have failed to note any direct effect of my essay on the trend 

 of biological thought. 



Among post-Darwinian controversies the one that has latterly 

 assumed the greatest prominence is that of the relative import- 

 ance of small variations in the way of more or less — " fluctua- 

 tions " — and of " discontinuous variations," or " mutations," as 

 De Vries has called them. Darwin attached more importance 

 to the latter in the first four editions of the Origin of Species 

 than in subsequent editions : he was swayed in his attitude, as 

 is well known, by an article of the physicist, Fleeming Jenkin, 

 which appeared in the North British Review. The mathematics 

 of this article were unimpeachable but they were founded on 

 the assumption that exceptional variations would only occur in 

 single individuals, which is, indeed, often the case among those 

 domesticated races on which Darwin especially studied the 

 phenomena of variation. Darwin was no mathematician or 

 physicist, and we are told in his biography that he regarded 

 every tool-shop rule or optician's thermometer as an instrument 

 of precision : so he appears to have regarded Fleeming Jenkin's 

 demonstration as a mathematical deduction which he was bound 

 to accept without criticism. 



Mr. William Bateson, formerly Professor of Biology in the 



^ A " hormone " is a chemical substance which, formed in one part of the body, 

 alters the reactions of another part, normally for the good of the organism. 



