NOMENCLATURE AND CLASSIFICATIONS. 163 



undulating membrane, as in Oscillaria. The organism creeps along, but at the same 

 time rotates around the long axis, mostly with a swinging of one or both free ends. 

 Habitat, hot sulphur springs and other fluids in which hydrogen sulphide is developed. 

 No reliable method is yet known for the separation of the species. The number and 

 size of the included sulphur-granules are not of specific value. They depend on the 

 amount of hydrogen sulphide in the water. 



2. Family RHODOBACTERIACEAE. 



Cell-contents rose, red, or violet, from the presence of bacteriopurpurin . Sulphur 

 granules are also included. 



Classification still very artificial, owing to imperfect knowledge. Author follows 

 Winogradsky. 



(I) Subfamily THIOCAPSACEAE. 



Cells united into families. Division of the cells in three directions of space. 

 Thiocystis Winogradsky. 



Families small, compact, enveloped singly or several together in a gelatinous 

 cyst, capable of swarming. When the families have reached a definite size they 

 escape from the gelatinous cyst, the latter either swelling and softening uniformly or 

 at some particular spot. The escaped cells either pass iuto the swarm stage or unite 

 into a larger fused complex of families, the individual cells of which separate and 

 swim away only after a long time, and by means of much vigorous struggling. 



Thiocapsa Winogradsky. 



Non-swarming, globose cells spread out upon the substratum in flat families, 

 which are loosely enveloped in a common gelatin. The membrane is split by the 

 growth of the family, and the cells are separated as if by the swelling of an inter- 

 mediate substance. 

 Thiosarcina Winogradsky. 



Non-swarming cells arranged in packet-shaped families, corresponding to the 

 genus Sarcina in the Eubacteriaceae. 



(II) Subfamily LAMPROCYSTACEAE. 



Cells united into families. Divisions of the cells, first in three and then in two 

 directions of space. 

 Lamprocystis Schroter. 



Families at first solid, then globose-hollow, becoming perforated net-form; cells 

 finally separating into small groups which are capable of swarming. 



(Ill) Subfamily THIOPEDIACEAE. 



Cells united into families. Divisions in two directions of space. 

 Thiopedia Winogradsky. 



Families tabular, formed of cells arranged in fours and capable of swarming. 



(IV) Subfamily AMOEBOBACTERIACEAE. 



Cells united into families. Division in one direction of space. 

 Amoebobacter Winogradsky. 



Cells connected by plasma threads. Families amoeboid motile. The cell families 

 slowly change form, the cells drawing together into a heap or spreading out widely, 

 thus bringing about a change in the shape of the whole family. In a resting condi- 

 tion a common gelatin is extruded, the surface of which becomes a firm membrane. 



