x INTRODUCTION 



fundamentally predatory behaviour. Although predatory species 

 may apparently, and for a time, live quite well, yet their temporary 

 success is at the expense of permanent survival. This teaching 

 is startling to Biologists, many of whom scoff at the idea of 

 morality or progress in connection with Evolution. 



I could myself scarcely have attained to the present outlook 

 but for the aid of special stepping-stones which, quite naturally, 

 led on to higher things. What was it that constituted these 

 stepping-stones ? The theses with regard to the Biology of 

 Food previously established by me. These theses briefly are to 

 the effect that (a) perpetual " in-feeding " produces a general 

 predisposition to disease, and (b) that the morbidity so estab- 

 lished eventually manifests itself in a tendency to monstrosity. 

 From these conclusions there emerged the corollary that 

 Parasitism not only differs from, but is fundamentally antithetic 

 to Symbiosis, i.e., systematic biological co-operation, and, what 

 is more, that Parasitism is as much abhorred and penalised by 

 Nature as Symbiosis is sanctioned and rewarded. In the sequel 

 I was led on to the broad view that organic evolution itself owes 

 its direction chiefly to a socio-physiological principle, namely, 

 that of " Symbiogenesis," and this view is to be further enforced 

 in the present volume. I have not yet come across a single 

 biological writer who distinguishes fitly between Symbiosis and 

 Parasitism. Yet this distinction is one, I venture to suggest, 

 upon which much, nay very much, in biological interpretation 

 depends. I do not think I am going beyond the facts in stating 

 that, with regard to this distinction, Science has as yet attained 

 no clarity of thought. 



Modern Biology is rather seriously handicapped by the lack 

 of an adequate and systematic co-ordination of the many lines 

 of evolution making up sociological development and also by 

 the absence of a comprehensive theory of disease. These 

 deficiencies become the more impressive the more one has had 

 occasion to envisage the wonderful, articulated economy of Nature 

 as exhibited by the phenomena coming under the head of 

 Symbiosis. Small wonder, therefore, that I have felt tempted 

 to expand my exposition of Symbiosis in the attempt to remedy 

 the, to me, most glaring defects of Biology. 



I trust that I am not unduly sanguine in hoping for an 

 early acceptance of my socio-physiological views, and that in 

 particular the antithesis between Symbiosis and Parasitism, to 



