i8o THEORETICAL BIOLOGY 



us that this assumption is erroneous. Just as with the genesis 

 of our implements, another rule comes in here, which is not 

 identical with the function-rule ; accordingly, to distinguish 

 between them, this must be called the rule of genesis. 



For two hundred years the dispute has raged as to whether 

 it is necessary to assume a special rule of genesis for living 

 things. Natural science, elsewhere so ready to apply the 

 analogy with machines, has here, strange to say, made an 

 exception. As soon as the spermatozoa were discovered, it 

 was thought perfectly obvious that here we had human 

 beings in miniature, which only had to grow to full size in 

 order to be completely developed. This was the foundation 

 of the later doctrine of " evolution," which saw in the genesis 

 of the organism merely a process of increase in size. 



The theory of spermatozoa-men was soon shown to be 

 wrong. Biologists then seized on the idea of plant-buds, 

 which not only grow, but must unfold in order to produce 

 leaves. And so arose the doctrine of unfolding or genesis or 

 " evolution.** 



This doctrine was opposed by Wolff, who, as a result of his 



exact observations, became convinced that in the genesis of 



the living organism there could be no question of a mere un- 



\ folding. For Wolff, genesis appeared as a perpetual creation 



of something new, an epigenesis. 



It is not necessary to follow into detail the dispute that 

 ensued, for in our own day Driesch has finally settled it in 

 favour of epigenesis. 



Epigenesis, being the more difficult doctrine to grasp, had 

 a hard battle to fight, but it conquered at last through the 

 overwhelming power of facts. Again and again the evolution- 

 ists attempted to maintain the dogma of an invisible frame- 

 work present in the germ from the beginning, by assuming 

 hereditary particles, which, in some way or other, were 

 spatially connected together. Finally there could no longer 



