Varietäten, Descendenz, Hybriden. 53 



for a consideration of the essential characteristics of such relations 

 of cause and effect. Pfeffer has emphasized the indirectness and 

 also the disproportionality of the response in relation to the 

 Stimulus; he interpolates an induced internal change as the 

 direct outcome of the external Stimulus and by this we gain the 

 idea of possible after-effects of this change and enduring change in 

 the organism. Jennings' experiments on Infusorians led him to a 

 similar point of new and he emphasizes the varying internal phy- 

 siological states of the organism as determining the nature of 

 its response to an external Stimulus. 



Morphological Change: The work of Vöchting, Goebel, 

 Klebs, Loeb, Herbst and Driesch has shown to what an extent 

 morphological change can be produced by alterations of environ- 

 ment. Klebs in particular brought out the unexpected degree to 

 which ontogeny is dependent on external Stimuli: he assumes a spe- 

 cific structure proper to each species with a ränge of potentialities 

 to be brought out by different external conditions. These produce 

 related changes of internal conditions which cause the reaction. 



Pfeffer, Klebs, Jennings and other workers all recognize that 

 the internal effect of Stimulation outlasts the Stimulus; so it is clear 

 that the internal State prevailing at any moment can be the result 

 of past experience. 



Semon has introduced the term Engram for such records of 

 former Stimulation left upon the organism, and, broadly speaking, 

 'engrams', 'physiological states' and 'internal conditions' are one and 

 the same thing. 



Habit illustrated by movement: The mnemic factor in the 

 movements of plants is illustrated by the periodic awakening of 

 sleeping plants in the absence of all light. This exemplifies the be- 

 ginning of a Habit, a capacity acquired by repetition of reacting to 

 a fraction of the original environmental Stimulus. This new capacity 

 is due to the mnemic Association of internal states each of which 

 originally required its independent Stimulus but now by organic 

 bonding the initiation of one of them automatically engenders the 

 whole series. 



Jennings has followed this acquisition of a habit in Stentor 

 and formulates the principle that "the resolution of one physiolo- 

 gical State into another becomes easier and more rapid after it has 

 taken place a number of times." 



The difificulties raised by psychologists at the transference of 

 the conception of Association from consciousness to these phe- 

 noma in lower animals and plants are met by the conviction that 

 in their reaction to environment man, plants, and all living things 

 belong indisputably to one and the same great class. 



Habit illustrated by Morphology: Ontogeny, being an 

 automatic series of morphological reactions in the absence of the ori- 

 ginal complete series of Stimuli is to be regarded as actually and 

 literally a habit. 



It has the characteristic of a habit in exhibiting fixity as regards 

 its main sequence and yet mobility as regards its minor and ter- 

 minal stages. It is in these latter only that ontogenetic variations occur. 



Hering was the first thinker to assert the similarity of the 

 rhythms of development and memory, usually formulated as the 

 identity of memory and inheritance. 



Semon Rignano and Darwin alike hold that it is memory 

 that bridges the gulf between successive generations and that Evolution 



