§ II. J Cell-groupings. 1 3 



compact gelatinous envelope which may fill entire vats with a 

 substance looking like frogs' spawn, and which will be con- 

 sidered again in a later lecture ; the term kefir-grains is applied 

 to the bodies employed by the inhabitants of the Caucasus in 

 the preparation from milk of a sourish beverage rich in car- 

 bonic acid. The kefir-grains are in the fresh living state white 

 bodies, usually of irregularly roundish form, equal to or ex- 

 ceeding a walnut in size. They have their surface crisped with 

 blunt projections, and furrowed like a cauliflower ; they are of a 

 firm toughly gelatinous consistence, becoming cartilaginous, 

 brittle, and of a yellow colour when dried, and are chiefly com- 

 posed of a rod-shaped Bacterium. The small rods are for the 

 most part united together into filaments, which are closely 

 interwoven in countless zig-zags and firmly connected together 

 by their tough gelatinous membranes. It must also be observed, 

 that the Bacterium-filaments are not the only constituents of the 

 granules ; numerous groups of a Sprouting Fungus like the 

 yeast-fungus of beer are enclosed between them, especially in 

 the periphery, living and growing in common with the Bacterium, 

 but in much smaller quantity, and taking only a passive part in 

 the formation of Zoogloeae. 



If Bacteria grow not in fluids but on some solid substance 

 which is only wet or moist, the grouping into Zoogloeae is a 

 frequent phenomenon even in those forms which separate 

 from one another in larger amounts of fluid owing to the 

 dehquescence of their gelatinous envelopes. The more limited 

 supply of water on the merely damp substratum is not 

 sufficient to make this gelatinous substance swell up to the 

 point of deliquescence. On decaying potatoes, turnips, and 

 similar substances we may often see small lumps of gelatinous 

 matter of a white or yellowish tint or of some other shade of 

 colour, and composed of these aggregations of Bacteria. These 

 lumps deliquesce in water. We have a special instance of the 

 kind in the often-described occurrence of the blood-portent, 

 Micrococcus prodigiosus (Monas prodigiosa of Ehrenberg), pro- 



