in.} THE MEANING OF EVOLUTION 259 



dissociated individuals, one life goes on moving: every- 

 where the tendency to individualize is opposed and at 

 the same time completed by an antagonistic and com- 

 plementary tendency to associate, as if the manifold 

 unity of life, drawn in the direction of multiplicity, made 

 so much the more effort to withdraw itself on to itself. 

 A part is no sooner detached than it tends to reunite 

 itself, if not to all the rest, at least to what is nearest 

 to it. Hence, throughout the whole realm of life, a balanc- 

 ing between individuation and association. Individuals 

 join together into a society; but the society, as soon as 

 formed, tends to melt the associated individuals into a new 

 organism, so as to become itself an individual, able in 

 its turn to be part and parcel of a new association. At the 

 lowest degree of the scale of organisms we already find 

 veritable associations, microbial colonies, and in these 

 associations, according to a recent work, a tendency to 

 individuate by the constitution of a nucleus. 1 The same 

 tendency is met with again at a higher stage, in the proto- 

 phytes, which, once having quitted the parent cell by way of 

 division, remain united to each other by the gelatinous 

 substance that surrounds them — also in those protozoa 

 which begin by mingling their pseudopodia and end by 

 welding themselves together. The "colonial" theory 

 of the genesis of higher organisms is well known. The 

 protozoa, consisting of one single cell, are supposed to 

 have formed, by assemblage, aggregates which, relating 

 themselves together in their turn, have given rise to 

 aggregates of aggregates; so organisms more and more 

 complicated, and also more and more differentiated, 

 are born of the association of organisms barely differ- 

 entiated and elementary.* In this extreme form, the 



> Cf. a paper written (in Russian) by Serkovski, and reviewed in the 

 Annie biologique, 1898, p. 317. 



* Ed. Perrier, Les Colonies animates, Paris, 1897 (2nd edition). 



