xviii Unconscious Memory 



sion to the misnomer of Wallace's book, " Darwinism," 

 that he introduces the term "Wallaceism " ^ for a theory 

 of descent that excludes the transmission of acquired 

 characters. This was, indeed, the chief factor that led 

 Charles Darwin to invent his hypothesis of pangenesis, 

 which, unacceptable as it has proved, had far more to 

 recommend it as a formal hypothesis than the equally 

 formal germ-plasm hypothesis of \\^eismann. 



Tlie chief difficulty in accepting the main theses of 

 Butler and Hering is one familiar to every biologist, and 

 not at all difficult to understand by the laj^man. Everyone 

 knows that the complicated beings that we term " Animals" 

 and " Plants," consist of a number of more or less indi- 

 vidualised units, the cells, each analogous to a simpler 

 being, a Protist — save in so far as the character of the 

 cell unit of the Higher being is modified in accordance ^^'ith 

 the part it plays in that complex being as a whole. Most 

 people, too, are familiar with the fact that the complex 

 being starts as a single cell, separated from its parent ; or, 

 where bisexual reproduction occurs, from a cell due to the 

 fusion of two cells, each detached from its parent. Such 

 cells are called " Germ-cells." The germ-cell, whether of 

 single or of dual origin, starts by dividing repeatedly, so 

 as to form the primary embryonic cells, a complex mass of 

 cells, at first essentially similar, which, however, as they 

 go on multiplying, undergo differentiations and migra- 

 tions, losing their simplicity as they do so. Those cells 

 that are modified to take part in the proper work of the 

 whole are called tissue-cells. In virtue of their activities, 

 their growth and reproductive power are limited — much 

 more in Animals than in Plants, in Higher than in Lower 

 beings. It is these tissues, or some of them, that receive 

 the impressions from the outside which leave the imprint 

 of memory. Other cells, which may be closely associated 



^ The term has recently been revived by Prof. Hubrecht and by 

 myself (Contemporary Review, November 1908). 



