ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 195 



of one organism in a certain medium is facilitated by the preseuce of 

 other bacteria Loth in the living and in the sterilised condition. For 

 example, the influenza bacillus was found to be easily cultivable, even 

 on pepton-agar plates, in conjunction with Gonococcus and B. diphtherias. 

 Sterilised cultures gave similar results, but the inoculations had to be 

 made directly, otherwise the growth was poor. From this the author is 

 inclined to think that the composition of the medium has little to do 

 with the promotion of growth, and that the influence is due to something 

 existing in the bodies of the bacteria. 



Bacterial Self-Purification of Streams. * — Dr. E. 0. Jordan, who 

 has made numerous and important observations on the bacterial self- 

 purification of streams, discusses the chief causes which are adduced as 

 the essential factors in the process. These are mechanical agitation and 

 aeration, dilution, the action of sunlight, the influence of plankton, sedi- 

 mentation, and the exhaustion of the food supply. Most importance is 

 assigned to the last two factors, and the author believes that in the 

 causes connected with insufficiency or unsuitability of the food supply 

 is to be found the main reason for the bacterial self-purification of 

 streams. 



Vitality of Acetifying Bacteria.f — E. C. Hansen, in a third memoir 

 on acetifying bacteria, deals with the limit of vitality of three species, 

 viz. B. aceti, B. pasteurianum, and B. kiitzingianum. In media such 

 as beer, double beer, 10 p.c. cane sugar, and distilled water, the limits 

 of vitality were found to be from over ten years (beer) to a few months 

 (water). Then follow some observations on the variation of these three 

 species, the test of variation and of their transformation being whether 

 the cells stained with iodine solution or not. 



Biology of Peptonising Milk Bacteria.:}: — The results of the re- 

 searches of 0. Kalischer on the action of an aerobic peptonising milk 

 bacterium are as follows. The milk-sugar is slowly diminished. The 

 bacteria did not produce a soluble ferment capable of inverting lactose ; 

 but a ferment which inverted cane-sugar was formed. The presence of 

 volatile acids, valerianic and acetic, was detected. Grape-sugar was more 

 strongly attacked by the bacteria than milk-sugar. In grape-sugar 

 solutions the bacteria grew throughout the whole depth of the medium, 

 but in lactose solutions only on the surface. The fat was not attacked, 

 and a diastatic ferment not formed. Casein was converted into albu- 

 mose, and later into pepton, ammonia, leucin, tyrosin, aromatic oxyacids, 

 volatile acids, and a mixture of bases, but no indol or phenol. The 

 ferment produced by the bacteria is practically identical with trypsin. 

 The rennet ferment formed by the bacteria had similar properties to 

 those of the ordinary rennet ferment. 



New Chromogenic Micrococcus.§ — Mary Hefieran describes a coc- 

 cus, Micrococcus roseus flavus, producing a salmon-pink pigment, which 

 was isolated from Mississippi river water on plates composed of " Nahr- 

 stoff Heyden " agar. 



* Joum. Exper. Med., v. (1900) pp. 271-314 (1 pi.). 



t CE. Trav. Laborat. Carlsberg, v. (1900) pp. 39-46. Cf. this Journal, 1895, p. 90. 

 t Arch. f. Hygiene, xxxvii. p. 30. See Beih. z. Bot. Centralbl., ix. (l'.KX)) p. 11. 

 § Bot. Gazette, xxx. (1900) pp. 261-72 (4 figs.). 



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