200 EVOLUTION, OLD AND NEW. 



prehensive conception of the nature of heredity and 

 adaptation, by giving us the term * memory ' conscious 

 or unconscious, for the continuity of Mr. Herbert 

 Spencer's polar forces, or polarities of physiological 



units. 



****** 



" The undulatory movement of the plastidules is the 

 key to the mechanical explanation of all the essential 

 phenomena of life. The plastidules are liable to have 

 their undulations affected by every external force, and, 

 once modified, the movement does not return to its 

 pristine condition. By assimilation they continually 

 increase to a certain point in size, and then divide, and 

 thus perpetuate in the undulatory movement of succes- 

 sive generations, the impressions or resultants due to 

 the action of external agencies on individual plastidules. 

 This is Memory. All plastidules possess memory ; and 

 Memory which we see in its ultimate analysis is iden- 

 tical with reproduction, is the distinguishing feature of 

 the plastidule ; is that which it alone of all molecules 

 possesses, in addition to the ordinary properties of the 

 physicist's molecule ; is, in fact, that which distin- 

 guishes it as vital. To the sensitiveness of the move- 

 ment of plastidules is due Variability to their 

 unconscious Memory the power of Hereditary Trans- 

 mission. As we know them to-day they may 'have 

 learnt little, and forgotten nothing' in one organism, 

 and ' have learnt much, and forgotten much ' in 

 another ; but in all, their memory if sometimes frag- 

 mentary, yet reaches back to the dawn of life upon the 

 earth. E. RAY LANKESTER." 



