4 



262 THEORETICAL BIOLOGY 



genesis of the individual organism from the germ, we are not 

 deaHng with an unfolding — "evolutio" — since in the 

 germ there is no framework lying ready prepared, and only 

 requiring to open out in order to give the finished animal. 

 On the contrary, the germ and the embryo are unfinished 

 structures, which are transformed into completed frameworks 

 only through invasion by impulse after impulse, working 

 in accordance with plan. By the formation of new folds, 

 the simple becomes complex. Thus we have to do with 

 a folding up, and not with an unfolding ; with a " cow- 

 plication," and not with an " ^A;plication." 



With species it is quite otherwise. There is no such 

 thing as an unfinished species (in the way that there are un- 

 finished single organisms), and there never has been. 



If by " species " we understand an association of different 

 individuals according to a plan, then such associations exist 

 both among organisms with complex and among organisms 

 with simple framework. The association, i.e. the method by 

 which the connection is effected, is the same in all cases. 

 When we consider together simultaneously the family organi- 

 sations of animals as they succeed one another, it is always 

 a chain ; when we separate them from one another, it is 

 always a network. 

 \ The more numerous the different genotypes within a 



species, the more readily do they seem to split off into different 

 races, which may then form new species. 



That is the only thing we can say with much probability 

 concerning the evolution of new species. All the rest is the 

 work of imagination. 



It does really mean something, then, when we speak of the 

 evolution of one species from another. We are then pictur- 

 ing the races as having been wrapped up within the species. 

 Or the species unfolds into different species when its races 

 separate from one another. 



