COMMUNAL ACTIVITY OF BACTERIA 261 



dyes, of which acid fuchsin is an example, is either to increase the 

 production of peroxide or to hinder the removal of normally pro- 

 duced amounts. 



"A bacterial colony may be merely a fortuitous result of con- 

 tinued multiplication, but it seems too to furnish a means whereby 

 numerous potentially nocuous influences are rendered less effective. 

 An isolated organism may produce diffusible substances as readily 

 as one within a colony, but it cannot retain them within its immedi- 

 ate neighborhood, and a high concentration of such substances can 

 only occur when numerous adjacent organisms collaborate in their 

 production. The most important peroxide destroying bodies have 

 been shown to be diffusible and will therefore reach a high concen- 

 tration only when a colony is formed. By their presence traces of 

 peroxide in excess of the amount which can be dealt with by the 

 oxidative mechanism of individual organisms are immediately de- 

 stroyed and in this way the viability of cells damaged by small 

 changes in the environment is retained. It may be considered as a 

 primitive maintenance of constant internal environment by ensur- 

 ing that the immediate toxic body in many cases of bacterial injury 

 (hydrogen peroxide) shall not accumulate. In this respect the bac- 

 terial colony may almost be regarded as a metazoan individual." 



This analogy between the bacterial colony and the metazoan in- 

 dividual does not mean that such colonies are on the evolutionary 

 high road which leads to multicellular individuals, but it does give 

 some insight into certain survival values which favored the develop- 

 ment of metazoans from cells which had these and other potentiaU- 

 ties. Similarly, the facts brought forward in the present compre- 

 hensive survey of the survival values of aggregations of organisms 

 indicate that groups of animals having such values have the possi- 

 bility of becoming what is usually known as ''social animals." To 

 be sure, they must possess other attributes. An aggregation implies 

 that the grouped individuals have tolerance for the presence of other 

 organisms in the same limited area, and that they have a reaction 

 system which causes them to aggregate or to remain aggregated if 

 passively collected. In addition certain other qualities are needed, 

 particularly the ability to establish close group integration. The 



