CONCLUSIONS AND SUGGESTIONS 181 



system is really the final expression of the primitive 

 dominance in the individual, it is conceivable that the 

 highly specialized nervous inhibition may have some- 

 thing in common with the primitive form of inhibition 

 in the lower animals and plants. 



ORIGIN OF METABOLIC GRADIENTS AND OF DOMINANCE 



The data of reconstitution discussed in chaps, iv 

 and v show very clearly that new metabolic gradients 

 arise in relation to various external factors: in Tubularia 

 the cut end (pp. 132-37); in Corymorpha the difference 

 between a free surface and one in contact (pp. 142-46) ; 

 in Harenactis difference in the character of a wound 

 determining more or less growth of new tissue and so 

 the localization of a new apical region. As regards the 

 plants, the evidence from adventitious buds (pp. 83-86) 

 also indicates that the axes of such buds arise anew, 

 slight differences in metabolic rate between different 

 cells apparently often determining whether a new indi- 

 vidual shall arise in one place or another. As regards 

 various plants, we know that certain of the minor axes, 

 and in some cases the major axis, are determined by 

 the differential action of light. I believe we are justi- 

 fied in saying that whenever a new metabolic gradient 

 of sufficiently high rate is established by an external 

 factor a new individuation occurs. 



It is of course easy to assume, as is often done, that 

 polarity and symmetry are self-determined in the in- 

 dividual, and that these self-determined relations are 

 simply altered and modified by external factors. But 

 the evidence for self-determination is lacking, and the 

 evidence for external determination is abundant and 



