54 LABORATORY BACTERIOLOGY 
3. GENERA BELONGING TO THE FAMILY SPIRILLACEE 
Cells rigid, not snakelike or flexuous. 
a. Cells without organs of motion . . I. Spivosoma 
6. Cells with organs of motion (flagella). 
(1) Cells with 1, very rarely 2 to 3, polar 
flagella . . . . . . 2, Microspira 
(2) Cells with polar lapel, in tufts 
_offrom5to2z20. . . . . . 3. Spirillum 
Cells flexuous . . . ae Gite sd . 4. Spirocheta 
4. GENERA BELONGING TO THE FAMILY CHLAMYDO- 
BACTERIACEE 
I. Cell contents without granules of sulphur. 
a. Cell threads unbranched. 
(1) Cell division always only ini plane 1. Streptothrix 
(2) Cell division in 3 planes previous 
to the formation of conidia. 
(2) Cells surrounded by a very 
delicate, scarcely visible, 
sheath (marine) . . .2. Phragmidiothrix 
(4) Sheath clearly visible (in 
fresh water). . . 3. Crenothrix 
6. Cell threads branched (pseudo 
branches) .. . . 4. Cladothrix 
II. Cell contents containing Saificie gran- 
ules . od Be Ro we BBs Dao 
5. GENERA BELONGING TO THE FAMILY BEGGIATOACEEX 
Only one genus known (Beggiatoa Trev.), which is scarcely 
separable from Osci/laria. Character as given under the family: 
Of these genera Streptococcus, Micrococcus, «Bacterium, 
Bacillus, Microspira, and Spirillum contain the most important 
of the pathogenic bacteria. The familiar genus Staphylococcus 
of older classifications is included in the genus Micrococcus by 
Migula. It is important that the distinguishing characters of 
these genera be thoroughly learned. 
