Protoplasmic Predisposition 427 



it is futile for us to try to find the cause of this " tendency," 

 just as it is hopeless, at a certain stage of chemical science, 

 to seek for the cause of " chemical affinity '* between two 

 given elements, or the reason for the different atomic weights. 



Protoplasmic Predisposition 



Many biologists have suggested the search for the mech- 

 anism of evolution in the very nature of protoplasm itself. 

 In the last decade of the Nineteenth Century a German biolo- 

 gist, Georg Pfeffer, extended his criticisms of the theory of 

 natural selection to emphasize the doctrine that living mat- 

 ter is self -directing and self-propelling. These two proper- 

 ties include the capacity for automatic variability in adaptive 

 directions. This was intended not as a mystic surrender of 

 the problem to vitalistic interpretation, but as an affirmation 

 of fundamental data for the biologist. Living matter has 

 indeed the capacity to assimilate to itself non-living physico- 

 chemical systems and to direct or control physico-chemical 

 processes to serve its own ends. Living matter has a physico- 

 chemical aspect, but it has also a conscious or purpose-serving 

 aspect. The connection between the two is unknown, and 

 perhaps beyond our reach; but both aspects must be sub- 

 jected to scientific study. 



We can at any rate accept the fact that living matter 

 does actually form progressively more complex aggregates. 

 There are single-celled plants and animals of many degrees 

 of complexity, and there are forms of colonial type, in which 

 there is aggregation but little or no differentiation or division 

 of labor. Among the algae and fungi there is already a 

 division in the aggregates of almost identical cells, between 

 the reproductive and the vegetative groups; and among the 

 vegetative cells, there is a division between the mechanical 

 tissues and the food makers. Similarly among animals, we 

 can see many grades of aggregation with corresponding de- 

 grees of differentiation, from the sponges up to the highest. 

 And at each level of aggregation we find emerging charac- 



