INTRODUCTION xv. 



evolves and safeguards those very modes of reciprocal 

 differentiation which we must recognise as the universal means 

 of the creation and elaboration of physiological and psycho- 

 logical values, including those which perhaps may be more 

 especially regarded as genetic in character and influence. In 

 other words, symbiosis is more than a mere casual and isolated 

 biological phenomenon : it is in reality the most fundamental 

 and universal order or law of life. So much so is this the case 

 that I claim the great principle underlying all Creative Life, 

 all Progressive Evolution to be that of " Symbio gene sis "; 

 i.e., the mutual production and symbiotic utilisation of bio- 

 logical values by the united and correlated efforts of organisms 

 of all descriptions. It is a well-known saying of Aristotle that 

 the City exists for the sake of its good citizens, and I would 

 apply it to the biological society, which also exists for its 

 "good" citizens those organisms, namely, which by 

 symbiotic endeavour at once earn the right of biological 

 citizenship and contribute to the welfare, permanence and 

 progress of their " society." 



The secret of progressive evolution, I contend, has always 

 consisted in the operation of an important economic or quasi- 

 economic principle such as that rendered emphatic by the 

 results of organised human labour. As a French sociologist 

 (Bougie) expresses it: " Tous ceux qui ont analyse les effets 

 de 1'organisation du travail I'ont remarque : la mise en 

 commun des forces individuelles engendre une force totale plus 

 grande que leur somme. Quelles qu'en soient les raisons 

 diverses, economies de temps et d'espace, entrainement et 

 adaptation reciproque des efforts, la combinaison des travaux 

 augmente leur efficacite." 



The accumulation and utilisation of biological capital, 

 being racial (phylogenetic) rather than individual (onto- 

 genetic) matters, it is important to trace the operation of these 

 principles in the phenomena of heredity and genetics, which 

 are to be regarded as a sort of racial nutrition, gestation in the 



