1. Family: Coccaceæ (Zopf) Migula, all cocci.
Non-flagellated, Non-motile
  • Genus 1. Streptococcus Billroth: division in one plane only ([Fig. 49]).
  • Genus 2. Micrococcus (Hallier) Cohn: division in two planes only ([Fig. 50]).
  • Genus 3. Sarcina Goodsir: division in three planes only ([Fig. 51]).
Flagellated, motile
  • Genus 4. Planococcus Migula: division in two planes only.
  • Genus 5. Planosarcina Migula: division in three planes only.
2. Family: Bacteriaceæ Migula, all bacilli.
  • Genus 1. Bacterium (Ehrenberg) Migula: no flagella; non-motile.
  • Genus 2. Bacillus (Cohn) Migula: flagella peritrichic ([Fig. 52]).
  • Genus 3. Pseudomonas Migula: flagella at the end: monotrichic, lophotrichic, amphitrichic ([Fig. 53]).
3. Family: Spirillaceæ Migula, all spirilla.
Cells stiff
  • Genus 1. Spirosoma Migula: non flagellated; non-motile.
  • Genus 2. Microspira (Schrœter) Migula: flagella one to three at the end ([Fig. 54]).
  • Genus 3. Spirillum (Ehrenberg) Migula: flagella more than three at the end ([Fig. 55]).
Cell flexible
  • Genus 4. Spirochæta Ehrenberg: motile; no flagella ([Fig. 56]).
4. Family: Chlamydobacteriaceæ.
Cells cylindrical in long threads and surrounded by a sheath. Reproduction also by gonidia formed from an entire cell.
  • Genus 1. Chlamydothrix Migula ([Fig. 57]).
  • Genus 2. Crenothrix Colin ([Fig. 58]).
  • Genus 3. Pragmidiothrix Engler.
  • Genus 4. Spherotilus (including Cladothrix).

ORDER II. THIOBACTERIA: SULPHUR BACTERIA.

Cells without a nucleus, but containing sulphur granules, may be colorless or contain bacteriopurpurin and be colored reddish or violet.

1. Family Beggiatoaceæ.