DIPHTHEROID ORGANISMS 35 



environmental conditions. In order to explain variations in bacterial 

 types it is necessary to consider both Darwin's theory and that of 

 deVries. The former conception is based on natural selection in which 

 such variations as are better adapted to the struggle for existence will 

 be perpetuated. The theory of deVries holds that the tendency toward 

 variation in the germ plasm may give rise to permanent variations as 

 opposed to fluctuating variations. 



When bacteriology was in its infancy it was a popular notion that 

 types could be transmuted readily from one into the other and back 

 again. Strange as it may seem the idea has been reborn and given 

 great impetus within recent years. Pleomorphism is highly developed 

 among the diphtheroids and it is in this group that much confusion has 

 arisen not only as a natural result of the well known overlapping of 

 closely related types, but chiefly because of the ease with which appar- 

 ently pure cultures of the organisms undergo changes in their mor- 

 phology. In none of the work presented has the technic been of such a 

 nature as to preclude error. Billings and Rosenow state that single 

 colonies of diphtheroids from Hodgkin's disease "in dextrose agar 

 which showed bacilli only in smears, yielded in subcultures a pure 

 culture of staphylococci aerobically and forms of the bacillus either 

 pure or in mixture anaerobically on the same medium. These facts 

 suggest strongly that the associated staphylococcus is derived from the 

 bacillus." Certainly, no evidence is given by the authors that the 

 single colonies were pure. There is only one method whereby the 

 fallacy may be precluded and that method was not used in this par- 

 ticular instance. It may or may not be true that the staphylococcus 

 was associated with the bacillus, but the word "derived" is misleading. 

 We know from common practice that a single colony even when 

 obtained from highly diluted plate cultures, does not necessarily repre- 

 sent the descendants of a single bacterial cell. Such a mistake was 

 made by Goodman when he claimed to have separated the diphtheria 

 organism into an acid-producing and an alkali-producing type by the 

 plate method, on the assumption that he had a pure line. 



I shall deal exclusively with C. enzymicus described and named by 

 Mellon. This organism exhibits the pleomorphism of most diph- 

 theroids but is of especial interest because of the remarkable morpho- 

 logical changes the author claims to have produced. He was able to 

 show a seeming relationship between the diphtheroids and the strepto- 

 cocci and described a method whereby he transformed the bacillary type 

 of diphthefoid into a coccus and back again. The old question of sta- 



