FACTS CONCERNING VARIATION 193 



a bacterium which divides once an hour passes through as many generations 

 in ten days as an annual plant does in 240 years. 



Hansen showed that Saccharomyces cerevisiae, S. ellipsoideus, S. Pasteurianus^ 

 &c., gradually lost the power of spore-production when cultivated at temperatures 

 at which growth was still possible, but not that of spore-formation. This peculiarity 

 is more readily fixed in some species than in others, and it was not found possible 

 to obtain a hereditarily asporogenous race of Saccharomyces Pasteurianus. In other 

 cases, however, the asporogenous character was retained during twelve years' culture \ 

 It is worthy of note that a power of spore-formation is always latent in fermenting 

 yeast. Hansen has also found that fixed varieties may be obtained differing from 

 the parent form in shape, fermentative power, and so forth. Since pure cultures 

 were used derived from a single cell, it is obvious that the results were not due 

 to the presence of several forms, of which an asporogenous variety gained the 

 upper hand under the special cultural conditions, and finally became the only 

 remaining form 2 . The same applies to results obtained from cultures derived from 

 a single bacterium cell. 



Roux 3 produced an asporogenous variety of Bacillus anthracis by adding 

 a little phenol to the culture medium, while Phisalix obtained the same result by 

 cultivation at 42 C, and under other conditions also 4 . Phisalix found that the 

 power of spore-formation returned at once, or after a few generations, when material 

 cultivated for a long time at 30 C., or for a short time at 42 C., was returned to 

 a lower temperature. The fixed asporogenous variety, however, retained this 

 peculiarity even after its virulence had been restored by passage through the body 

 of an animal. Migula was able to produce an asporogenous variety of Bacterium 

 ramosum by continued cultivation in the presence of phenol, but did not succeed 

 with other forms 5 . 



In certain bacteria the suppression of the power of pigment or poison-formation is 

 hereditary not only by vegetative, but also by sporogenous reproduction. It is also 

 possible that the power of enzyme production may be eliminated 6 , and conversely 

 Hansen states that varieties of yeast may be raised which have an increased 

 fermentative activity 7 . 



Changes of shape may also be rendered permanent in Saccharomyces and in 



1 Hansen, Meddelelser fra Carlsberg Laboratoriet, 1896, IV, Heft 2, Re'sume, p. 67 ; 

 Centralbl. f. Bact., 1895, 2. Abth., I, p. 858; 1898, IV, p. 89; 1899, V, p. 5 ; Compt. rend. d. 

 Laboratoire d. Carlsberg, 1900, T. v, p. I. Cf. also Klocker and Schionning, Centralbl. f. Bact., 

 1898, 2. Abth., IV, p. 460, and Klocker, ibid., 1900, VI, p. 241. 



2 Beyerinck, Centralbl. f. Bact., 1898, 2. Abth., IV, p. 657 ; 1897, III, p. 449. 



3 Roux, Ann. d. 1'Inst. Pasteur, 1890, T. iv, p. 25. See also Behring, Zeitschr. f. Hygiene, 

 1889, Bd. vi. 



* Phisalix, Compt. rend., 1892, T. cxiv, p. 684; T. cxv, p. 253. Cf. also Surmont and 

 Arnould, Ann. d.l'Inst. Pasteur, 1894, T. vill, p. 817, and the literature quoted by Migula, System 

 der Bacterien, 1897, I, p. 179. 



5 Migula, 1. c. 



6 Cf. the contradictory statements of Dubourg, Compt. rend., 1899, T. cxxvill, p. 440, and 

 A. Klocker, Centralbl. f. Bact., 1900, 2. Abth., VI, p. 241. 



7 An accommodation and after-effect as regards fermentative activity was observed by Dienert, 

 Ann. d. 1'Inst. Pasteur, 1900, T. xiv, p. 139. 



PFEFFER. II Q 



