September 25, 1908] 



SCIENCE 



387 



and inheritance.^ Hering says that "be- 

 tween the me of to-day and the me of yes- 

 terday lie night and sleep, abysses of un- 

 consciousness ; 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 mo- 

 ment to limit myself to asserting the iden- 

 tity of ontogeny and habit, or, more 

 generally, to the assertion in Semon 's 

 phraseology, that ontogeny is a mnemie 

 phenomenon. 



Evolution, in its modern sense, depends 

 on a change in the ontogenetic rhythm. 

 This is obvious, since if this rhythm is ab- 

 solutely 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. A habitual action, for in- 

 stance, a trick learned by a dog, may be 

 altered by adding new accomplishments; 

 at first the animal will persist in finishing 

 his performance 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. 



^Everyone who deals with this subject must 

 take his stand on the foundation laid by Hering 

 in his celebrated address given at Vienna in 1870 

 and reprinted in No. 148 of Ostwald's " Exakt 

 Klassiker." The passage quoted (p. 14) is from 

 Samuel Butler's translation of Hering in " Un- 

 conscious Memory," 1880, p. 110. Butler had 

 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 transmissibilitg des earact6res acquis," 

 Paris, 1906. 



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 appar- 

 ently 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 possibil- 

 ity 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 Gal- 

 ton 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 conceiv- 

 ably occur in memory or habit, that is, the 

 rhythm as a whole may be altered by some 

 cause acting on the nerve-centers con- 

 nected with the earlier links of the series. 

 The analogy is not exact, but such an 

 imaginary case is at least of a different 

 type from a change in habit consisting in 

 the addition of a new link or the alteration 

 of one of the latest formed links. If we 

 were as ignorant of the growth of human 

 actions as we are of variation, we might 

 have a school of naturalists asserting that 

 all changes of habit originate in the earl- 

 iest link of the series. But we know that 

 this is not the case. On the other hand, I 



° Goebel's " Organography of Plants," part II., 

 p. 285. 



