Skptembee 18, 1908] 



SCIENCE 



359 



look at the phenomena of movement or 

 those of structure. If this is allowable — 

 and the weight of evidence is strongly in 

 its favor — a conclusion of some interest 

 follows. 



If we reconsider what I have called the 

 indirectness of stimulation, we shall see 

 that it has a wider bearing than is at first 

 obvious. The "internal condition" or 

 "physiological state" is a factor in the 

 regulation of the organism's action, and it 

 is a factor which owes its character to 

 external agencies which may no longer 

 exist. 



The fact that stimuli are not momentary 

 in effect but leave a trace of themselves 

 on the organism is in fact the physical 

 basis of the phenomena grouped under 



consider it probable that the nucleus plays in the 

 cell the part of a central nervous system? In 

 plants there is evidence that the ectoplasm is the 

 sensitive region, and, in fact, plays the part of 

 the cell's sense-organ. The change that occurs in 

 the growth of a cell, as a response to stimulus, 

 would on this scheme be a reflex action dependent 

 for its character on the structure of the nucleus. 

 The " indirectness " of stimulation would then 

 depend on the reception by the nucleus of the 

 excitation set up in the ectoplasm, and the sec- 

 ondary excitation reflected from the nucleus, lead- 

 ing to certain changes in the growth of the cell. 

 If the nucleus be the bearer of the past history 

 of the individual, the scheme here sketched would 

 accord with the adaptive character of normal 

 reactions and would fall into line with what we 

 know of the regulation of actions in the higher 

 organisms. Pfeffer ( " Physiology of Plants," 

 Eng. trans.. III., p. 10) has briefly discussed the 

 possibility of thus considering the nucleus as a 

 reflex center, and has pointed out difficulties in 

 the way of accepting such a view as universally 

 holding good. Delage ( " L'H6r6dit6," 2d edition, 

 1903, p. 88 ) gives a good summary of the evidence 

 which induces him to deny the mastery of the cell 

 by the nucleus. Driesch, however ( " Analytische 

 Theorie der organischen Entwicklung," 1894, p. 

 81 ) , gives reasons for believing that the cyto- 

 plasm is the receptive region, while the nucleus 

 is responsible for the reaction, and it is on this 

 that he bases his earlier theory of ontogeny. 



memory in its widest sense as indicating 

 that action is regulated by past experience. 

 Jennings^" remarks: "In the higher ani- 

 mals, and especially in man, the essential 

 features in behavior depend very largely 

 on the history of the individual; in other 

 words, upon the present physiological con- 

 dition of the individual, as determined by 

 the stimuli it has received and the reactions 

 it has performed. But in this respect the 

 higher animals do not differ in principle, 

 but only in degree, from the lower organ- 

 isms. ..." I venture to believe that this 

 is true of plants as well as of animals, and 

 that it is further broadly true not only of 

 physiological behavior, but of the changes 

 that are classed as morphological. 



Semon in his interesting book, "Die 

 Mneme,"^^ has used the word Engram for 

 the trace or record of a stimulus left on 

 the organism. In this sense we may say 

 that the internal conditions of Pfeffer, the 

 physiological states of Jennings and the 

 internal conditions of Klebs are, broadly 

 speaking, Engrams. The authors of these 

 theories may perhaps object to this sweep- 

 ing statement, but I venture to think it is 

 broadly true. 



The fact that in some cases we recognize 

 the chemical or physical character of the 

 internal conditions does not by any means 

 prevent our ascribing a mnemic memory- 

 like character to them, since they remain 

 causal agencies built up by external condi- 

 tions which have, or may have, ceased to 

 exist. Memory will be none the less mem- 

 ory when we know something of the chem- 

 istry and physics of its neural concomi- 

 tant. 



^P. 124 (1904). 



^ " Die Mneme, als erhaltendes Prinzip ira 

 Wechsel des organischen Geschehens," von Rich- 

 ard Semon, Ite Auflage, Leipzig, 1904; 2te Auflage, 

 1908. It is a pleasure to express my indebtedness 

 to this work, as well as for the suggestions and 

 criticisms which I owe to Professor Simon per- 

 sonally. 



