4 THE BIOLOGICAL PROBLEM OF TO-DA Y 



merit could find no foothold alongside the apparent 

 logical consistency of the theory of preformation. 



Wolff 's T/ieoria Generationis (1759) failed to 

 convince his contemporaries, because he could bring 

 against the closed system of the evolutionists only 

 isolated observations, and these doubtful of inter- 

 pretation ; and because, in his time, on account of 

 the rudimentary state of the methods of research 

 in biology, men attached more importance to ab- 

 stract reasoning than to observation. His effort 

 was the more praiseworthy in that it was observa- 

 tion bearing witness against abstract and dogmatic 

 conceptions. By means of actual observation he 

 tried to expose the fallacy in preformation, to show 

 that the organism was not fully formed in the germ, 

 but that all development proceeded by new forma- 

 tion, or epigenesis ; that the germ consisted of 

 unorganised organic material, which became formed 

 or organised only little by little in the course of its 

 development, and that Nature really was able to 

 produce an organism from an unorganised material 

 simply by her inherent forces. 



It is interesting to display the essential contrast 

 between preformation and epigenesis in the poetical 

 words of Wolff' himself. ' You must remember,' 

 so run his words in the second argument against 

 the probability of preformation, ' that an evolution 

 would be a phenomenon formed in its real essence 

 by God at the Creation, but created in condition 

 invisible, and so as to remain invisible for long 

 before it would become visible. See, then, that a 

 phenomenon of enfolding is a miracle, differing 



