Cells without a nucleus, but containing sulphur granules, may be colorless or contain bacteriopurpurin and be colored reddish or violet. 1. Family BEGGIATOACEÆ. Genus 1. _Thiothrix_ Winogradsky. „ 2. _Beggiatoa_ Trevisan. Of interest since it is without a sheath, is motile, but without flagella (Fig. 59). 2. Family RHODOBACTERIACEÆ. This has five subfamilies and twelve genera, most of which are due to the Russian bacteriologist Winogradsky who did more work than anyone else with the sulphur bacteria. THE CLASSIFICATION OF THE SOCIETY OF AMERICAN BACTERIOLOGISTS. The Committee on Classification of the Society of American Bacteriologists at the meeting held in December, 1919, submitted its final report. This report has not been formally adopted as a whole, but in all probability will be substantially as outlined below. This outline does not attempt to give the detailed characterizations of the different groups as defined by the committee, but does show the names to be applied to the commoner organisms. These organisms are included in the 4th and 5th orders. Details of the first three orders have not been worked out. They are listed merely for completeness. CLASS SCHIZOMYCETES. Unicellular, chlorophyl-free plants, reproducing by transverse division (some forms by gonidia also). ORDERS: A. Myxobacteriales--Cells united during vegetative stage into a pseudo-plasmodium which passes over into a highly developed cyst-producing resting stage. B. Thiobacteriales--Sulphur bacteria. C. Chlamydobacteriales--Iron bacteria and other sheathed bacteria. D. Actinomycetales--Actinomyces, tubercle and diphtheria bacilli. E. Eubacteriales--All the other common bacteria. GENERA OF ORDERS D AND E. D. ACTINOMYCETALES-- FAMILY I. ACTINOMYCETACEÆ Buchanan, 1918. Genus 1. _Actinobacillus_, Brampt, 1900. Type species, _Actinobacillus lignieresi_ Brampt, 1900. Genus 2. _Leptotrichia_ Trevisan, 1879. Type species, _Leptotrichia buccalis_ (Robin, 1847) Trevisan. Genus 3. _Actinomyces_ Harz, 1877. Type species, _Actinomyces bovis_ Harz. Genus 4. _Erysipelothrix_ Rosenbach, 1909. Type species, _Erysipelothrix rhusiopathiæ_ (Kitt, 1893) Rosenbach, swine erysipelas. FAMILY II. MYCOBACTERIACEÆ Chester, 1897. Genus 1. _Mycobacterium_ Lehmann and Neumann, 1896. Type species, _Mycobacterium tuberculosis_ (Koch, 1882) L. and N. Genus 2. _Corynebacterium_ Lehmann and Neumann, 1896. Type species, _Corynebacterium diphtheriæ_ (Loeffler, 1882) L. and N. Genus 3. _Fusiformis_ Hoelling, 1910. Type species, _Fusiformis termitidis_ Hoelling. Vincent’s angina. Genus 4. _Pfeifferella_ Buchanan, 1918. Type species, _Pfeifferella mallei_ (Loeffler, 1896) Buchanan. Glanders bacillus.