Figure 1. Layout of the apparatus used by Miller and Urey to produce organic compounds from “volcanic gases”. Products were identified by gas chromatography. Examples: A, asparagine; B, glycine; C, alpha-alanine; D, beta-alanine; E, alpha-aminobutyric acid. (Diagram: Anne Kemmling, Goettingen, Germany.)

Figure 2. Phototrophic bacteria. (a) Light micrograph of the phototrophic bacterium Chromatium okenii. The refractive sulfur globules inside the cells can be seen as well as the tuft of very powerful flagellae (micrograph: Michael Hoppert, Goettingen, Germany). (b) Bloom of the sulfur purple bacterium Amoebobacter purpureus at a depth of 7 meters (23 ft) in Lake Mahoney (British Columbia, Canada). (Photograph: Joerg Overmann, Munich, Germany, already published in Brock, Biology of Microorganisms, with permission of author, M. T. Madigan.)