Organisms arranged singly, in pairs and in irregular clusters; rarely in chains Peptococciis p. l^^l^. Note: Peptococcus constellatus may belong to Peptostrepiococcus. 23. Gram-negative, kidney-shaped to hemispherical cells occurring basically in pairs with the flat sides adjacent; animal parasites Neisseria p. 4S0 Note: Micrococcus morrhuae and M. roseus are described as Gram-negative occurring singly and in pairs. Not as above 24 24. Organisms arranged in cubical packets Sarcina p. Ifil Organisms from liquids are arranged singly, in pairs or as tetrads and occasionally in short chains; tetrads common in acid media; produce at least 0.5 to 0.7 per cent acid in yeast-extract-glucose-tryptose-phosphate broth, lowering the pH below 4.0; lactic acid produced is optically inactive; found in fermented liquids and foods Pediocoecus p. 529 Not as above 25 25. Organisms arranged in pairs only or in chains of varying lengths when growing in liquid media 26 Organisms arranged singly, in pairs and in clusters in liquid media; occasional species are motile 28 26. Organisms produce gas in Eldredge tubes when growing in yeast-extract-glucose-tryp- tose-phosphate broth; lactic acid produced is levo -rotatory; frequently produce a copious slime (dextran) in sucrose broth Leuconostoe p. 531 Not as above; lactic acid produced is dextro-rotatory 27 27. Parasitic; cells usually in pairs, particularly in pathological material, where they are encapsulated; chains are common in culture media; bile-soluble; found in the respira- tory tract of man Diplococcus p. 507 Other than above; parasitic or saprophytic Streptococcus p. 508 28. Cells occur predominantly as tetrads and are encapsulated in body fluids; occur as tetrads and in irregular masses in cultures Gaffkya p. ^66 Not as above Micrococcus p. 1^.55 Staphylococcus p. Ifil^ Note: Placed in the genus Staphylococcus are two species, Staphylococcus aureus and Staphylococcus epidermidis. Reference should be made to the species de- scriptions for separation from the other micrococci. 29. Cell masses are green or yellowish green; probably contain chlorobium chlorophyll and not bacteriochlorophyll 30 Cell masses red or purple; proceed to Section J p. 1031 30. Spherical to ovoid cells occurring in chains and forming flat sheets in which the chains are parallel. Oxidize hydrogen sulfide but do not store sulfur inside the cells Pelodictyon p. 63 Spherical cells united in loose trellis-like aggregates. Sulfur is deposited internally Clathrochloris p. 64
