354 SYMBIOGENESIS 



of mind upon the organism with which it is connected and 

 through which it operates, and the consequent importance of 

 symbiogenesis even in the evolution of mind. It is, of course, 

 obvious that the main considerations upon which I lay stress 

 in this, as in former volumes, viz., the importance of co-opera- 

 tion, service and exchange of surpluses, apply equally in the 

 world of mind, and can be read (by whoso will) into any work 

 dealing with the synthesis of human percepts into their higher 

 forms of combination. 



Incidentally I have thought it useful briefly to consider 

 Samuel Butler's theory concerning mind and design in Nature, 

 especially as put forward in Luck or Cunning, which is 

 acknowledged as his most mature production. 



Psychology recognises that the control of thought, equally 

 with the control of movement, requires effort, and, further, 

 that there is in Psychology as in Biology what may be called a 

 principle of progressive differentiation or specialisation, and 

 this, as well as the facts of reproduction and association, 

 suggests a symbiogenetic explanation. 



We have already noted that it is symbiogenetic evolution 

 that makes possible margins of capital which are indispensable 

 for higher developments of various kinds. Knowledge, 

 sympathy, altruism, mutual aid and reciprocal differentiation 

 can progress only in proportion as security of life purchased 

 by symbiotic labours is on the increase. 



We have also seen that individuality and consciousness 

 have very deep roots, and that they are present, at least 

 incipiently, in the most primitive forms of life. We have 

 inferred that plantagens, for instance, and also the phagocytes 

 in our body possess a kind of individuality, a kind of con- 

 sciousness. We also found both plantagens and phagocytes 

 to be busy members of symbiotic unions, i.e., active agents of 

 symbiogenesis. It seems as though all forms that can be seen 

 to figure at all independently in symbiogenesis have also this 

 in common, viz., that they are all endowed with a conscious- 

 ness, similar in kind though different in degree. It seems, 



