Human Infancy and the Recapitulation Theory 85 



action; it has reduced it, permeated it, and substituted for it; 

 that is, essentially altered it rather than supplemented it. As 

 Lankester puts it, plasticity can rise only as instinct yields it 

 place. It is customary, therefore, to speak of the involuntary 

 instinctive motor expressions, those discussed by Darwin and 

 other students of the emotions as remnants of older and more 

 complete action systems. With what degree of justice this 

 assumption is made is a question, for the evolution of skill is a 

 comparatively neglected topic. Students of the animals have 

 thus far been chiefly concerned with the problems relating to 

 animal intelligence. 



Still, there is probably no counterpart to the genetic sequence 

 from native excitant to meaning on the side of motor control. 

 In fact the situation seems just reversed. For phylogenetically 

 there was a progression from stereotyped behavior to less and 

 less fixed modes of behavior. Ontogenetically the progression 

 is from a few established modes to an indefinite number of adapted 

 voluntary habits. And these acquired habits cannot be homol- 

 ogous with the instinctive phylogenetic action systems, for 

 the very good reason that motor plasticity was evolved for the 

 express purpose of substituting better and different action systems 

 for them. 



There is, however, the possibility that there may be examples 

 of recapitulation among the various types of inherited modes of 

 movement: the automatic visceral control, the involuntary 

 accompaniments of the emotions, (fear, joy, grief, "expression")* 

 the random movements of early infancy, and the true reflexes. 

 With respect to the first two, so far as the writer is aware, there 

 are no essential differences between youth and maturity excep- 

 ting such as are induced by habit with the second, and none that 

 requires an ancestral explanation. Mumford 3 * advanced the 

 theory that the random movements of early infancy, associated 

 with the gradual ripening of the lower centers, are reminiscent in 

 certain cases of ancient aquatic modes of action. The suggestion 

 is perhaps a possible one without being at all convincing, and 

 surely the resemblance is not conspicuous. Besides, as Miss 

 Shinn notes, in commenting on the suggestion, many of the 

 movements such as the asymmetrical movements of the eyes, 



Brain, Vol. XX, 1897. 



