CONFORMITY WITH PLA^ 295 



at the same moment. Let us imagine, in an earthworm, 

 for instance, that the development of the germinal areas pro- 

 ceeds so equally that we finally have before us an animal 

 which, in all essentials, already has the form of the completed 

 animal, but consists entirely of protoplasm. A protoplasmic 

 animal of this kind consists entirely of independent genetical 

 building-stones, which, it is true, are spatially contiguous, but 

 do not exercise the slightest influence on one another. If 

 we remove from one of these a portion of the material, it 

 will restore its own shape from the remains of the protoplasm, 

 without any regard to its neighbours. Indeed, as Harrison 

 showed, one can remove an entire genetical building-stone — 

 for instance, the rudiment for the sciatic nerve — without in 

 any way checking the development of the rest of the limb. 



Now the effect of the critical point expresses itself in every 

 cell of each germinal area, in such a way that the gene present 

 in it becomes active and allows its specific framework to 

 crystallise out of the protoplasm. At one stroke a fully 

 developed earthworm, with all its functions, is got from the 

 protoplasmic worm. And therewith the genetical building- 

 stones have disappeared, which consisted of protoplasm alone : 

 in their place functional building-stones have come in, con- 

 sisting of framework -f protoplasm. 



What has now become of the impulse-systems which, in 

 complete independence, each governed a genetical building- 

 stone ? The boundaries of the completed organs, i.e. of the 

 functional building-stones, are quite different from those of 

 the germinal areas. Are the impulse-systems subject to the 

 same rearrangement, or not ? As we know from Wessely's 

 experiments, at the critical point there occurs a rearrange- 

 ment of the impulse-systems also. The genetical impulse- 

 systems have vanished ; in their place have come functional 

 impulse-systems, controlling the animal's growth. 



The earthworm need not fear that when some repair of 



