THE GENESIS OF LIVING ORGANISMS 215 



structure of a nerve-cell, a muscle-cell, a bone-cell, and 

 so forth. 



The difhculty we experience in understanding how the 

 form-giving genes work, lies in this, that, although they are 

 tied to a definite place in each individual cell, yet they must 

 act according to a system which is not present anatomically, 

 although it embraces a whole germinal area with many 

 hundreds of cells. 



But this difficulty disappears when we realise that it is / 

 only the material basis of the genes that is of necessity bound 

 to a definite position in space, whereas their non-material 

 portion, the impulse, is not bound in this way. 



The impulse always plays an active part, now stimulating 

 a gene, and now an anti-gene. An impulse, which is not fixed 

 to a definite position in space, may easily be connected up 

 with other impulses into a system. 



An impulse-system can allow a whole series of cells to 

 be simultaneously invaded by a fermentative action leading 

 to a certain chemical change. In the same way this change 

 can release in the same set of ceUs a fermentation which 

 brings about a certain change in their position ; this change 

 in position presents no difficulty, in view of the mobile foam- 

 structure of protoplasm. If we admit this, the sudden advent 

 of the polar systems ceases to be incomprehensible. The polar 

 system of directing points is then just a system of impulses, 

 in which each gives guidance in a different direction in space. 



Simultaneous and equipotential impulses of this kind 

 must produce in a mass of similar cells a differentiation 

 with regard to position, by prescribing a definite direction 

 for the movements of each, the result of which will be that 

 even the most amorphous conglomeration must take shape. 

 The number of cells within the mass is quite immaterial for 

 the achievement of the final form ; and this is in agreement . 

 with the results derived from experiment. 



