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The occurrence of deeply stained large round bodies in bacterial cultures has long been known. These large bodies have aroused much speculation, but from the study of the literature nothing definite can be learned concerning their nature and functions, and the majority of bacteriologists regard them as products of degeneration. The author has previously pointed out (1939a) that the large bodies which give the characteristic appearance to the cultures of L1 and of the pleuropneumonia group of organisms are morphologically very similar to the large bodies of bacteria and are probably analogous in nature. If this supposition is correct, we must obtain more information concerning the nature of the large bodies in order to understand the nature of L1 and of the pleuropneumonia group of organisms and their relationship to other microorganisms. The large bodies in most cultures degenerate without further development. It is not unreasonable to expect that in some cultures their functions will be apparent if we study a large number of cultures belonging to different species. With this thought in mind, many routine bacteriological cultures have been examined during the last three years for the occurrence of large bodies. When they were found, their properties and their eventual development was studied both in the original cultures and in transplants. Between 3,000 and 6,000 cultures were examined although their exact number is not known since no records were kept of the cultures which showed no, or only a few, large bodies. By this procedure strains which produced large bodies in abundance were found in many bacterial species. They occurred only occasionally among freshly isolated strains of Escherichia coli, Hemophilus influenzae and Hemophilus parainfluenzae, gram-positive aerobic sporebearing bacilli and Streptococcus. Colonies in which nearly all cocci transformed into large bodies were frequently seen in gonococcus cultures grown directly from patients, and all strains of 1 The expenses of this investigation have been defrayed in part by a grant from the Commonwealth Fund. This is publication 57 of the Robert W. Lovett Memorial.

A few bacterial species axe characterized by a peculiar pleomorphism, consisting in the gradual swelling of the bacteria into large fusiform or round bodies. A similar transformation occurs in a few exceptional strains belonging to the common species under normal conditions of cultivation. Sublethal doses of lithium, calcium, chromium, mercuric salts and penicillin often produce similar forms. Glycin seems to be very effective in this respect (Gordon and Gordon, 1943). Observations described in previous papers (Dienes, 1942) indicate that the large bodies, if they are appropriately transplanted, will germinate in certain cultures. Usually they do not reproduce bacteria of normal shape, but a peculiar granular growth which was discovered by Klieneberger in cultures of Streptobacillusmoniliformis and named L1 (Klieneberger, 1935). A similar germination of the large bodies was observed in some strains of Escherichia coli, Hemophilus influenzae and BaciUus funduliformis. An L type of growth was observed also in cultures of Neisseria (Dienes, 1940) and of a Flavobacterium. The large bodies germinated, according to our observations, only in spontaneously pleomorphic strains, not in cultures made pleomorphic by toxic influences. It was pointed out in the above-mentioned paper (Dienes, 1942) that the L type of growth is not the only direction in which the large bodies develop. Sometimes they reproduce bacteria of regular shape and size. One of the authors observed this process in E. coli (Dienes, 1939) and recently in a clear form in a strain of Streptobacius

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Two strains of L forms of group A streptococci were examined for group-specific polysaccharide and found to lack this substance. One of these was found to make a substance that had several properties in common with M protein. It is suggested that the absence of the cell wall polysaccharide is responsible for the lack of rigidity of the L form and that the L form of this species closely resembles protoplasts as prepared from other species.