Vol. 120,no. 2, p. 800, column 1, sentence beginning on line 10 should read. "The intensity of a peak at 404 nm was 35% of that at 435 nm, whereas that of all other mercury lines down to 239 nm was less than 10-6%."

Surface carbohydrates of Mycoplasma mycoides var. capri were made visible by the cytochemical staining procedure with concanavalin A, horseradish peroxidase, and diaminobenzidine.

Anionic sites on mycoplasma membranes were visualized in the electron microscope by a polycationized ferritin derivative. The technique of thin sectioning was used. Staining prior to fixation led to clustering of ferritin granules on the mycoplasma cell surface. On glutaraldehyde-fixed Mycoplasma mycoides subsp. capri, M. gallisepticum, M. pneumoniae, and Acholeplasma laidlawii, the anionic sites were uniformly distributed over the entire membrane surface. M. hominis did not bind the polycationic ferritin label. Chemical and enzymatic treatments of the mycoplasmas indicated that the anionic sites may be lipid phosphate groups. Isolated M. mycoides subsp. capri membranes were labeled exclusively on only one membrane surface, presumably the outer one. Liposomes prepared from diphosphatidylglycerol and phosphatidylcholine were also labeled by the polycationic ferritin.

Phosphatidylglycerol is the main component (87%) of the membrane phospholipids of Mycoplasma hominis. It is immunologically active. Antibodies directed against phosphatidylglycerol were detected in rabbits intravenously immunised with native M. hominis or isolated M. hominis membranes. The intravenous method of immunisation was chosen in order to select for a response to surface antigenic determinants. Anti-phosphatidylglycerol antibodies were induced in rabbits by intravenously injecting the flocculated complexes of methylated bovine serum albumin and a phosphatidylglycerol/phosphatidylcholine/cholesterol mixture. These antibodies were specifically bound to intact M. hominis, as shown by complement fixation and Coombs tests. Native M. hominis were not agglutinated by anti-phosphatidylglycerol antibodies; but after partial digestion of the membrane proteins with Pronase, the mycoplasmas were heavily agglutinated by the anti-phosphatidylglycerol antibodies. The same amount of anti-phosphatidylglycerol antibodies was bound to intact M. hominis, containing 600 Mg of phosphatidylglycerol as to OMg of phosphatidylglycerol in the optimal conflgurational arrangement of a mixed phosphatidylglycerol/phosphatidylcholine/cholesterol micelle. It is concluded that the major part of the phosphatidylglycerol in native M hominis membranes is masked, probably by membrane proteins, and is not accessible to the anti-phosphatidylglycerol antibodies. Immunologische Untersuchungen zur Lokalisation von Phosphatidylglycenn in Mycoplasma hominis -Membranen.Zusammenfassung: Die Zellmembran von Mycoplasma hominis enthält als Hauptphospholipoid das immunologisch aktive Phosphatidylglycenn. Bei Kaninchen, die intravenös mit intakten M hominis und isolierten Membranen vonAf. hominis immunisiert worden waren, wurden Antikörper gegen Phosphatidylglycenn nachgewiesen.Anti-Phosphatidylglycerin-Antikörper reagierten mit intakten M. hominis (Komplementbindungsreaktion). Intakte M. hominis wurden durch AntiPhosphatidylglycerin-Antikörper nicht agglutiniert; jedoch wurden die Anti-Phosphatidylglycerin-Antikörper spezifisch adsorbiert (CoombsTest). Nach partiellem Abbau der Membranpro-

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