326 Plant Life and Evolution 



F. Darwin borrows from Seman the word 

 " engram " to indicate the effects of a stimulus 

 upon the protoplasm, and Darwin argues that these 

 engrams are permanent and transmissible from cell 

 to cell. As he explains it the engrams, or results 

 of stimulation, are of the nature of memory. " My 

 view is that the rhythm of ontogeny is actually and 

 literally a habit. It undoubtedly has the feature 

 which I have described as preeminently character- 

 istic of habit, viz., an automatic quality which is 

 seen in the performance of a series of actions in 

 the absence of the complete series of stimuli to 

 which they (the stages of ontogeny) were originally 

 due. This is the chief point on which I wish to 

 insist: It means that the resemblance between on- 

 togeny and habit is not merely superficial, but deeply 

 seated. ... It cannot be denied that the onto- 

 genetic rhythm has the two qualities observable in 

 habit namely, a certain degree of fixity or auto- 

 maticity, and also a certain variability. It is not 

 irrevocably fixed, but may be altered in various 

 ways. Parts of it may be forgotten or new links 

 may be added to it. In ontogeny the fixity is espe- 

 cially observable in the earlier, the variability in 

 the later, stages." 



Darwin's mnemic theory does not involve the 

 assumption of special determinants or pangenes, and 

 as we have already pointed out in Chapter II, the 

 similarity in the constitution of the egg, and the sub- 

 jection of the developing embryo to practically iden- 



