xxii. SYMBIOGENESIS 



master, and that its use must be strictly in accordance with 

 bio-economic requirements, i.e., with symbiogenetic needs. 



The abhorrence of Nature to indiscriminate and pre- 

 daceous (non-reciprocal) modes of nitrogen-getting is clearly 

 expressed, as I have shown, in the bad cumulative effects of 

 perpetual "in-feeding" and in the more acute ill-effects, as 

 evidenced by the clinical symptoms coming under the head 

 of anaphylaxis or serum-disease (the modifications of the cells 

 of an organism by the injection of "dissimilar" albuminoid 

 substances so that they seem to react with greater intensity on 

 the repetition of the injection). Perpetual in-feeding I believe 

 to be on the road to Pathogenesis, which is the antithesis of 

 Symbiogenesis. Most important bio-economic and evolu- 

 tionary principles are here involved, and the more I pursue 

 this study the more I am forced to conclude that we have as 

 yet but touched the fringe of Evolution. 



That some such principle as Orthogenesis, i.e., progressive 

 variation along a definite line, is widely operative in Nature, 

 has of late increasingly suggested itself to our leading 

 biologists, but I believe I am justified in saying that it has 

 never before been as fully and convincingly demonstrated as 

 by my symbiogenetic theory, how bio-economic factors provide 

 a definite and persistent principle for the accumulation of 

 variations. Symbiogenesis thus explains and complements 

 Orthogenesis, or, at any rate, there is no progressive Ortho- 

 genesis (in a truly qualitative sense) without Symbiogenesis. 



The importance of Symbiogenesis in the domains of 

 mind and of Psychogenesis generally is very great, 

 and throughout parallel to that which it bears to the 

 creation of physiological and genetic values. If I have but 

 scantily or fragmentary dealt with this subject in 

 Chapter VII., I hope that, at any rate, my treatment will 

 prove of suggestive value in particular to physiological 

 psychologists. There should be no antagonism between 

 psychologists and physiologists or evolutionists. 



The wholesome criticism applied by Samuel Butler to the 



