224 CLASSIFICATION OF THE MICRO-ORGANISMS. 



very rapidly. This deposit often spreads along the 

 threads which run in the deeper part of the gelatine, 

 or sends here and there fine threads into the deeper 

 layers of the gelatine. In the puncture and stroke culti- 

 vations the same appearance is repeated ; in the deeper 

 part a delicate network of threads is formed, but this is 

 soon obscured by the more quickly growing superficial 

 layer; this network spreads out from the inoculation 

 track in the form of rays like the plume of a feather. 

 This organism has as yet only been met with once, and 

 then as an accidental impurity. 



Pigment- Some rarer cocci which attract attention by the pro- 



mfcrococci Auction of colouring material may also be mentioned 

 here, although they are for the most part as yet insuffi- 

 ciently known, and do not perhaps all belong to the 

 micrococci. (M. cinnabareus, flavus, &c., see above ; 

 Micrococcus prodigiosus, see Bacillus prodigiosus.) 



Micrococcus luteus* Cells about I/*, in diameter, elliptical, 

 highly refracting. Form yellow drops, 1 3 mm. in diameter, 

 on slices of cooked potato; on fluid substrata they form thick, 

 yellow, wrinkled skins. The pigment is insoluble in water. 



Micrococcus aurantiacus. Oval bodies, 1 5 p.. in diameter, 

 occurring singly or united in pairs, in fours or in zooglaea 

 masses. Orange-yellow spots, which finally form an unin- 

 terrupted layer, especially on boiled white of egg ; a thick, 

 golden-yellow layer on nutrient solutions. Colouring matter 

 soluble in water. 



Micrococcus chlorinus. Occurs in the form of a finely 

 granular zooglsea ; forms yellow or greenish layers on nutrient 

 solutions and boiled eggs. Colouring matter soluble in 

 water, decolourised by acids. 



Micrococcus cyaneus. Elliptical spheres, giving to nutrient 

 solutions and slices of potato an intense blue colour. The 

 colouring matter is very similar to that of litmus ; it is 

 soluble in water, becomes red with acids, and again assumes 

 the blue colour on neutralisation of the acid by ammonia. 



Micrococcus violaceus. Elliptical cells, larger than Mio. 

 prodigiosus, often united in chains, form violet blue gela 

 tinous clumps and patches on boiled potatoes. 



* All described by Schroter, Cohn's Beitrdge zur Biologic der Pflanzen. 

 Bd. 1, Heft 2. 



