16 president's address. 



Hering says that ' between the me of to-day and the me of yestef- 

 day lie night and sleep, abysses of unconsciousness ; nor is there any 

 bridge but memory -with which to span them.' And in the same way 

 he claims that the abyss between two generations is bridged by the 

 unconscious memory that resides in the germ cells. It is also the same 

 as that of Semon and to a great extent as that of Rignano.^ I, however, 

 prefer at the moment to limit myself to asserting the identity of ontogeny 

 and habit, or, more generally, to the assertion in Semon's phraseology, 

 that ontogeny is a mnemic phenomenon. 



Evolution, in its modern sense, depends on a change in the onto- 

 genetic rhythm. This is obvious, since if this rhythm is absolutely fixed, 

 a species can never give rise to varieties. This being so, we have to ask 

 in what ways the ontogenetic rhythm can be altered. An habitual action, 

 for instance, a trick learned by a dog, may be altered by adding new 

 accomplishments ; at first the animal will persist in finishing his per- 

 formance at the old place, but at last the extended trick will be bonded 

 into a rhythm of actions as fixed as was the original simpler performance. 

 May we not believe that this is what has occurred in evolution ? 



We know from experiment that a plant may be altered in form by 

 causes acting on it during the progress of development. Thus a beech 

 tree may be made to develop different forms of leaves by exposing it to 

 sunshine or to shade. The ontogeny is different in the two cases, and 

 what is of special interest is, that there exist shade-loving plants in 

 which a structure similar to that of the shaded beech-leaf is apparently 

 typical of the species, but on this point it is necessary to speak with 

 caution. In the same way Goebel points out that in some orchids the 

 assimilating roots take on a flattened form when exposed to sunlight, but 

 in others this morphological change has become automatic, and occurs 

 even in darkness. - 



Such cases suggest at least the possibility of varieties arising as 

 changes in or additions to the later stages of ontogeny. This is, briefly 

 given, the epigenetic point of view. 



But there is another way of looking at the matter — namely, that 

 upheld by Galton and Weismann. According to this view ontogeny can 

 only be changed by a fundamental upset of the whole system — namely, 

 by an alteration occurring in its first stage, the germ cell, and this view 

 is now very generally accepted. 



The same type of change may conceivably occur in memory or habit ! 

 that is, the rhythm as a whole may be altered by some cause acting on 

 the nerve-centres connected with the earlier links of the series. The 



Butler's translation of Hering in Unconscious Memory, 1880, p. 110. Butler hait 

 previously elaborated the view that ' we are one person with our ancestors' in his 

 entertaining book Life and Habit, 1878, and this was written in ignorance of 

 Bering's views. 



' Sur la tratismissiblliie des earacteres acquis, Paris, 1906. 



' Goebel's OrganofjrapTiy of Plants, part ii. p. 285. 



