290 THEORETICAL BIOLOGY 



by the control, for cell-division cannot be effected by any 

 mechanical rule of working. 



Even where Nature is active in super-mechanical ways, 

 there is no arbitrariness anywhere, but always law. A law, 

 however, which is also design of the most exalted kind, and 

 which casts its spell over the entire process. 



DIRECTION 



Invasion by the impulses always means a new formation 

 of framework, and consequently is always referable to an 

 influence exerted by the genes on the protoplasm ; the proto- 

 plasm, as a result of this influence, either itself begins to move, 

 or else transforms protoplasmic bridges into nervous paths 

 of conduction. 



If we look at the entire nervous system of an animal at 

 the beginning of a reflex action, we see everywhere the peri- 

 pheral routes for excitation and the bridges leading from centre 

 to centre. These structures, however, are invariabty accom- 

 panied by protoplasm, containing nuclei with genes, ready to 

 repair any damage that may arise by forming new structure. 



At the beginning of the non-reflex actions, the intra- 

 central bridges are not quite complete, and accordingly must 

 be re-formed from time to time by the influence of the impulses. 

 It looks like an ingeniously woven net, in which, however, 

 at certain spots, whether in the mark-organ or the action- 

 organ, some meshes are missing that are of decisive import- 

 ance for the path that the excitation shall follow. These 

 bridges are re-formed each time, and then again broken down. 

 The re-forming of the meshes is not fixed mechanically, and 

 does not follow an automatic rule of working ; it depends on 

 the direction, which is also subject to laws, but of a super- 

 mechanical kind. 



Let us imagine that on a ship which is to follow a certain 



