58 BIOLOGICAL ASPECTS OF HUMAN PROBLEMS 



there is a close parallelism between the processes 

 concerned in the development of cell memory in its 

 widest sense and the processes concerned in the de- 

 velopment of the impregnated egg cell. This view, 

 first clearly stated by Hering in his famous Vienna 

 address in 1870, has been elaborated by Semon, and 

 very recently Mr. Francis Darwin has given it in- 

 genious if not convincing support. The growth of 

 the individual from the germ cell is through a series 

 of stages of cell division, the process of each stage 

 acting as stimuli to a further unfolding, "each unit 

 following its predecessor like the movements linked 

 together in an habitual action performed by an ani- 

 mal." There is, indeed, much to be said in favor 

 of the idea that the rhythm or progression of in- 

 dividual development or ontogeny is essentially a 

 habit. This rhythm or progression certainly has 

 the characteristic feature of habit, the automatic 

 property visible in the execution of a series of 

 actions in response to a mere fraction of the series of 

 stimuli on which these actions the successive stages 

 of ontogeny originally depended. But the pro- 

 gressions of ontogeny and habit resemble each 

 other not merely in this fundamental quality of 

 variability. "A habit," says Mr. Darwin, "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 especially 

 observable in the earlier, the variability in the later, 

 stages." This quality of variability is extremely 



