656 SUMMARY OF CURRENT RESEARCHES RELATING TO 



galactina imetropha Sette, or Bacteridium prodigiosum Schrot.) ; and 

 Sehnetzler believes Eabenhorst's Palmella mirifica, described as 

 occurring in similar situations, to be but a form of Cohn's Micrococcus 

 prodigiosus ; the differences in the size of the cells and in the color- 

 ation being due to its occurrence on an animal instead of a vegetable 

 substratum. The presence or absence of a gelatinous matrix is no 

 distinctive character between the two species. During the formation 

 of the red gelatinous matter on the meat, the temperature varied 

 between 25° and 30° C. Cold alcohol extracted the colouring matter ; 

 the rose-coloured solution became greenish yellow on addition of 

 ammonia, acids colouring it red. Spectrum analysis showed a broad 

 absorption-band in the green. 



We have therefore here a chromogenous Schizomycete which 

 possesses the remarkable property of producing colouring matters 

 from the elements derived from the substratum and from the air at a 

 suitable temperature. 



New Bacterium sensitive to Light.* — Among the Schizomycetes 

 which T. W. Engelmann has previously studied, with respect to the 

 action of light, only one was sensitive to this action. This form, 

 called on account of its colour, Bacterium chlorinum,\ disengaged 

 oxygen in the light, and probably for this reason was attracted to 

 the light when oxygen was deficient. He found, last year, a second 

 form Bacterium photometricum, which reacted in a very high degree 

 under the influence of light. It is slightly reddish in colour. The 

 microspectroscopic eye-piece shows a powerful absorption of all the 

 rays whose wave-length is less than 0*62 p, especially those between 

 • 62 and • 59 (orange). 



The influence exercised by light on B. photometricum differs very 

 remarkably, in many respects, from that shown by other motile 

 organisms. 



In the first place the rapidity of the movements depends on it. 



In light of constant intensity the rapidity of the movements is, 

 generally, in direct proportion to the luminous intensity ; more rapid, 

 ceteris paribus, in the ultra-red and orange of the light of the sun or 

 of gas, than in the other regions of the spectrum. 



In the case of prolonged action of light, especially of an intense 

 light (and chiefly of the ultra-red and orange), the greater number 

 of the bacteria become quiescent, this taking place directly when the 

 ventilation is imperfect. This repose may be disturbed (all the 

 quicker when it has been of shorter duration) not only by darkening, 

 or a change of colour which acts in the same way, but also by any 

 appreciable increase of light. 



When the luminous intensity diminishes suddenly, or when its 

 quality (the wave-length) undergoes a change acting in the same way, 

 the bacteria quickly retire, then stop for a time, and presently recom- 

 mence their movements. 



The positive changes of the intensity or of the colour of the light do 



* Eev. Internat. Sci. Biol., ix. (1882) pp. 469-70. 

 t See this Journal, ante, p. 380. 



