president's address. 25 



Still another code of communication Beems to me to be at least con- 

 ceivable. One of the most obvious characteristics of animal life is the 

 guidance of the organism by certain groups of stimuli, producing either a 

 movement of seeking (positive reaction') or one of avoidance (negative 

 reaction). Taking the latter as being the simplest, we find that in 

 the lowest as in the highest organisms a given reaction follows each 

 one of a number of diverse conditions which have nothing in common 

 save that they are broadly harmful in character. We withdraw our 

 hands from a heated body, a prick, a corrosive substance, or an electric 

 shock. The interesting point is that it is left to the organism to discover 

 by the method of trial and error the best means of dealing with a sub- 

 injui-ious stimulus. May we not therefore say that the existence of 

 pleasure and pain simplifies inheritance 1 It certainly renders unnecessary 

 a great deal of detailed inheritance. The innumerable appropriate move- 

 ments performed by animals are broadly the same as those of their 

 parents, but they are not necessarily inherited in every detail ; they are 

 rather the unavoidable outcome of hereditary but unspecialised sensitive- 

 ness. It is as though heredity were arranged on a code-system instead of 

 by separate signals for every movement of the organism. 



It may be said that in individual life the penalty of failure is pain, 

 but that the penalty for failure in ontogenetic morphology is death. But 

 it is only because pain is the shadow cast by Death as he approaches 

 that it is of value to the organism. Death would be still the penalty of 

 creatures that had not acquired this sensitiveness to the edge of danger. 

 Is it not possible that the sensitiveness to external agencies by which 

 structural ontogeny is undoubtedly guided may have a similar quality, 

 and that morphological variations may also be reactions to the edge of 

 danger. But this is a point of view I cannot now enter upon. 



It may be objected that the inheritance of anything so complex as 

 an instinct is diflBcult to conceive on the mneroic theory. Yet it is impos- 

 sible to avoid suspecting that at least some instincts originate in indi- 

 vidual acquirements, since they are continuous with habits gained in the 

 lifetime of the organism. Thus the tendency to peck at any small object 

 is undoubtedly inherited ; the power of distinguishing suitable from un- 

 suitable objects is gained by experience. It may be said that the engrams 

 concerned in the pecking instinct cannot conceivably l)e transferred from 

 the central nervous system to the nucleus of the germ- cells. To this I 

 might answer that this is not more inconceivable than Weismann's 

 assumption that the germ-cell chances to be so altered that the young 

 chicken pecks instinctively. Let us consider another case of what 

 appears to be an hereditary movement. Take, for instance, the case of a 

 young dog, who in fighting bites his own lips. The pain thus produced 

 will induce him to tuck up his lips out of harm's way. This protective 

 movement will become firmly associated with, not only the act of fighting, 



t f'l^tt ,1pnr)inf,s, Jiehtifior of /!ie Lmirr Or<inii'sniH. 



