552 The Philippine Journal of Science wis 



DISCUSSION 



As stated above, variations in the fermentative characteris- 

 tics of cultures have been observed by many w^riters. By most 

 authors this phenomenon has been regarded as a mutation such 

 as De Vries observed in higher plants, in that the new races 

 seem to appear suddenly and in a relatively small number of 

 individuals and the new characteristics are constantly trans- 

 missible. Pringsheim,'*" however, regards a new characteristic 

 such as the faculty of fermenting a given sugar as an adaptation 

 to a new environment simply. Since sex and body cells are not 

 separated in bacteria as in higher organisms, it is theoretically 

 possible that such a new environment may impress upon the cells 

 a characteristic which persists in the absence of the special 

 stimulus. Such adaptive variations are not mutations in the 

 sense of De Vries. Benecke " holds similar views regarding the 

 adaptive character of variations of the Bacterium coli mutabile 

 type. Burri,^^ after extensive experiments on Bacterium coli 

 mutabile and B. coli imperfectum, holds that the new fermenta- 

 tive characteristic may be exhibited by the descendants of all 

 individuals of the parent stem, while in the mutations of De 

 Vries they are present in only from 1 to 3 per cent. Further, 

 he concludes from his experiments that the characteristic is, in 

 strict sense, not new, but a latent characteristic become active. 

 It is gradually acquired, while the De Vries mutation arises 

 suddenly and fully formed. Josef Klein,^^ working with Bac- 

 terium coli mutabile, confirms the work of Burri and regards 

 these variations as adaptations gradually acquired rather than 

 mutations in the ordinary use of the term. Baerthlein ^* holds 

 that the above-described sudden appearance of new characteris- 

 tics in strains of bacteria are true mutations. Such mutations, 

 often indistinguishable from atavisms, have usually occurred in 

 his experiments as the result of a change from a less favorable 

 medium, such as is found in old agar or bouillon cultures, or in 

 fasces, to a more favorable medium, as fresh agar. In other 

 cases, the addition of various substances to the medium and the 

 growth at high temperatures or the multiplication in the body 

 of an infected animal seem to favor the production of mutations 



Med. Klinik (1911), 7, 144. Also, Die Variabilitat niederer Organis- 

 men. Berlin (1910). 



" Zeitschr. f. induct. Ahstammungs- u. Vererbungslchre (1909), 2, 215. 

 ''Centralbl f. Bakt. etc., II Abt. (1910), 28, 321. 

 ' Zeitschr. f. Hyg. u. Infektionskrankh. (1912), 73, 87. 

 " Arb. a. d. kais. Gesundheitsamte (1912), 40, 433. 



