The physiological and general characters of 123 strains of Listeria were examined, and 33 of these were compared, in a computerized numerical analysis, with Erysipelothrix, Streptococcus, Corynebacterium, Microbacterium, Arthrobacter, Jensenia, Brevibacteriurn, Cellulomonas and Kurthia. It was concluded that Listeria and Erysipelothrix are distinct monospecific genera, not closely related.On physiological grounds, Listeria bore the nearest resemblance to faecal streptococci, and Erysipelothrix to other streptococci.

SUMMARYThe antigenic structure of Haemophilus vaginalis (Gardner & Dukes, Edmunds, and h i e s & Jones strains) was compared by means of geldiffusion precipitin reactions with that of H . injlwenxae and Corynebacterium cervicis (Laughton). Haemophilus vaginalis (Amies & Jones) was closely related to H . injluenzae, and formed a group with related species; H . vaginalis (Gardner & Dukes) and C . cervicis formed separate groups; but all three groups possessed common antigenic components.These strains of bacteria are among those reported as being related to Mycoplasma hominis, and their antigenic relationships are thus of importance in this connexion.

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SUMMARY: Two strains of bacteria which produced flagella when grown at 36" but not at 44" were examined ; one was a strain of Salmonella typhimurium and the other of Proteus vulgaris. These organisms were grown on membranes for electron microscopy, being incubated at 36" so that the parent bacteria of each microcolony possessed a normal quota of flagella, and then transferred to 44" so that no more flagella were produced. In the microcolonies, after several divisions, it appeared that all these flagella were retained by the original parents, in accordance with the theory that bacteria of this type divide by budding from a growing-point at one pole.The suggestion that the main growth of the cell envelopes in unicellular bacteria is from a growing-point a t one pole was deduced from the behaviour of the flagella in dividing bacteria by Bisset (1951). It was found that in some cases one daughter had few flagella or none, whereas the other had a full complement ; in other cases there appeared to be a progressive diminution in degree of development and age of the flagella from the point of division to the tip of one daughter, whereas once more the other daughter had all its flagella M l y developed. At the putative growing-point the cell wall also appeared to be thinner and less well developed than over the remainder of the cell, and i t could be shown to contain a relatively high concentration of basophilic material, presumably nucleoprotein.Further evidence in support of this concept has been obtained from a variety of sources. Bergersen (1953) described the behaviour of similar growing points in Escherichia coZi when their polarity of growth was so disturbed by cultivation in the presence of chloramphenicol that side-branches were produced instead of polar buds. Malek, Voskyova, Wolf & Fiala (1954), by means of cinematography, confirmed the concept that bacteria of this type grow from one pole. The corollary, that multicellular septate bacteria grow from the points of junction of cell wall and cross-wall, i.e. from the tips of each component cell (Bisset, 1953) was confirmed by Tomcsik (1956) with his elegant micro-serological technique.However, it was suggested by Stocker (1956) and by Qua.dling & Stocker (1956) that growth of the cell wall is diffuse and not localized a t a growing point. These authors based their conclusions mainly upon the behaviour of a strain of SaZmoneZZa typhimurium which produced flagella at 37" but not at 44". Cultures were grown for a period a t 37" and then transferred to 44" so that no more flagella were produced, although growth and division continued. When examined by Leifson's flagellar stain, the appearance of these cultures suggested that the flagella had not been retained by a small number of bacilli, representing those which already possessed them at the end of their period of growth