SOME FINAL CONSIDERATIONS 183 



character of an epigenesis. The spatial structure is not pre- 

 formed in the egg, but it arises de novo in the development of 

 each individual. We must not forget, however, that in another 

 form the multiplicity is already present in the egg, viz. as in- 

 tensive multiplicity. But for this intensive multiplicity of the 

 egg, its further development would be inconceivable. The spatial 

 multiplicity of the egg, therefore, does not arise from nothing 

 at all, but rather by the transformation of intensive into ex- 

 tensive multiplicity. In other words, the structural plan is 

 potentially present in the egg already, though not, it is true, 

 in a spatial form; it is actualised during development. Ultima- 

 tely, all developmental processes can be referred back to the 

 constitution of the egg, from which they follow according to 

 fixed laws. This is the cause of their harmonious interlinking, 

 which is so essential for the normal course of development. The 

 orderly character of development, therefore, is due to the 

 constant composition of the egg, which is given once and for all. 

 The secret of development lies in the composition of the 

 fertilised egg; from it, all the rest follows of necessity. 



It can easily be understood that the consideration of the 

 phenomena of development, in which the marvellously perfect 

 structure of the organism seems to arise from nothing, has 

 given rise to questions regarding the nature of this great 

 mystery: Life. The very first investigations in the field of 

 "developmental mechanics" were designed to shed some light 

 on this problem. Roux, the "father of developmental mechanics", 

 himself adhered to the then dominant ''machine theory'* of life, 

 which regarded the living organism as nothing but a well 

 functioning machine. On this view, all biological phenomena 

 would be explicable entirely by means of the laws of physics 

 and chemistry. The egg, too, was regarded as such a complicated 

 machine; its development would be nothing but the setting 

 in motion of a wound-up clockwork. Weismann's theory, which 

 we have discussed above (p. 34), followed this train of thought 

 to its final logical conclusion. 



A campaign against these conceptions was started by Driesch. 

 His experiments, in particular those on sea urchins, had con- 

 vinced him that the machine theory could not explain the 



