ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 495 



(16,777,220); at the end of two days this bacterium will have 

 multiplied to the incredible number of 281,500,000,000 ; at the end of 

 three days it will have finished forty-seven trillions ; at the end of 

 about a week, a number which can only be represented by fifty-one 

 figures. 



In order to render these numbers more comprehensible, let us seek 

 the volume and the weight which may result from the multiplication 

 of a single bacterium. The individuals of the most common species 

 of rod-bacteria present the form of a short cylinder having a 

 diameter of a thousandth of a millimetre and about one five-hundredth 

 of a millimetre in length. Let us represent to ourselves a cubic 

 measure of a millimetre. This measure would contain, according to 

 what we have just said, 633,000,000 of rod-bacteria without leaving 

 any empty space. Now, at the end of twenty-four hours, the bacteria 

 coming from a single rod would occupy the fortieth part of a cubic 

 millimetre ; but at the end of the following day they would fill a 

 space equal to 442,570 of these cubes, or about half a litre. Let us 

 admit that the space occupied by the sea is equal to two-thirds of the 

 terrestrial surface, and that its mean depth is a mile, the capacity of 

 the ocean will be 928,000,000 of cubic miles. The multiplication 

 being continued with the same conditions, the bacteria issuing from a 

 single germ would fill the ocean in five days."* 



New Coloured Bacterium.! — Like similar discoveries, that of 

 Dx'. C. Bergonzini was made accidentally. An open vessel con- 

 taining a solution of egg-albumen had been left for about a montli 

 untouched, and its liquid was then found to have assumed a greenish- 

 yellow colour, and a thick dark violet-coloured pellicle covered the 

 surface. 



The colour was due to a bacterium, which, however, diff'ered 

 from the known purple CJiromococcus violaceus in being insoluble 

 in water ; the pellicle consisted of a Mycoderma, made up of 

 small violet bacteria, which exhibited decided movements when 

 isolated in the liquid ; they were cylindrical, and measured • 6 /a 

 to 1 /A in diameter, 2 yu, to 8 ft in length. Though the colour is 

 insoluble in water, it is readily dissolved by alcohol, which takes a 

 deep blue colour from it, leaving it whitish ; ether dissolves out with 

 difficulty a red-violet colouring matter, which is also insoluble in 

 water. The pellicle and the alcoholic solution both become green 

 when treated with hydrochloric acid ; nitro-hydrochloric acid alters 

 it to a pale yellow by a process of reduction. Strong caustic 

 potash dissolves out a light red colouring matter. The addition of 

 ammonia to the blue dilute alcoholic solution produces an opalescence, 

 followed by precipitation of greyish-violet flakes. A moderately 

 strong alcoholic solution, 8 mm. thick, examined with the spectro- 

 scope, showed complete absorption of the yellow and orange in the 

 spectrum, and a small absorption line between Fraunhofer's C and D. 

 These reactions, and those of the red form, described by Ray 



* Loc. cit., pp. 124-6. 



t AtinuLirio Soc. Nat. Modeiia. xiv. (1880) pp. 140-58. 



2 L 2 



