96 DISSOCIATIVE ASPECTS OF BACTERIAL BEHAVIOR 



Another manner in which dissociative reactions may reveal themselves in cultures 

 is, as just intimated, the generation of secondary or "daughter-colonies" occurring in 

 a background of primary culture. Instances of this phenomenon were given added 

 significance in 1906 and 1907 through the observations of Neisser and Massini on B. 

 coll mutabile, and similar observations were soon made on many forms. All these cases, 

 manifesting the spontaneous origin of new culture types within the old culture mass, 

 were quickly seized upon as indications of true mutations among the bacteria; and 

 this false conception persists in the minds of many bacteriologists, even at the present 

 day. 



Secondary colonies may be few or numerous ; sometimes one only, or again there 

 may be several hundred discrete bodies. As the number increases, howexer, they 

 blend more and more into the mass of mother culture and thus lose their colonial iden- 

 tity — at least macroscopically. Microscopically they may still be traced as "granula- 

 tions" of varying size, until the culture mass becomes a fine mosaic of the two or more 

 culture elements. Sometimes the secondary colonies arise near the surface and form 

 the well-known "papillae." Again they lie deeply imbedded in the culture, or even 

 in the medium itself, as in the case of S.fecalis, and do not register on the contour of 

 the primary colony. In some species (S.fecalis — Faith Hadley)' both forms of second- 

 ary colony may be observed, and in this case they appear as entirely different culture 

 types. 



The most common forms of secondary colony relate to centers of O or R type 

 culture arising in a background of S culture. On the other hand, it appears from the 

 older work of Preisz- and Pesch-' on B. anthracis, and from the more recent studies of 

 Anna Dulaney on B. coli, that secondary, S type colonies may arise in R type cul- 

 tures. In Dulaney's case they were generated particularly at the free margins of the 

 type R colonies after a prolonged growth. Tertiary colonies arising within the second- 

 ary have also been occasionally observed, particularly by Preisz^ for B. anthracis. The 

 whole subject of secondary and tertiary colony formation may possess additional in- 

 terest in its bearing upon the nature of the bacteriophage reaction, and with special 

 reference to the homogamic theory which I have briefly outlined in a previous publi- 

 cation.'' Here it was suggested that the resistant colonies which d'Herelle, Bordet, and 

 others have termed "secondaries" (arising in the lytic sites on agar, or in culture fil- 

 trates) may, in reality, be tertiary colonies arising after the disappearance of the sec- 

 ondaries. In this case the characteristic lytic plaques would be regarded as the sites 

 of disappearance of colonies of the secondary type, which itself might represent one of 

 the intermediate forms of culture. 



For the present we may leave the subject of the secondary colonies with the con- 

 clusion that these formations are of considerable significance as indicating that, hidden 

 in the mass of mother culture, regardless of the type concerned, there may exist cer- 

 tain centers where small or large groups of organisms, quite different from the mother 

 culture in form and physiology, have arisen and where they are carrying on their inde- 



' Personal communication. 



'Preisz, H.: Cenlralbl. f. Bak'.eriol, Abt. I, Orig., 35, 280. 1904; also 53, 510. 1911. 



3 See Hadley, Philip: loc. cil. ■* Personal communication. s Preisz, H.: loc. cit. 



^ See Hadle}', Philip: loc. cil. See also: Arch, oj Path, and Lab. Med. 1928. In press. 



