The fine structure of Nocardia asteroides was investigated by means of electron microscopy of thin sections. No differences were noted in the internal organization of bacillary and coccoid forms. A characteristic feature of the surface structure was the presence of the irregularly thick cell envelope associated with the cell wall. The outer surface of the cell wall often merged into the cell envelope. Cell division and branching occurred in a similar way as that in other actinomycetes. Separation of the hypha into daughter cells seemed to be caused by dissolution of the envelope between the apposed cross walls. The cytoplasm was closely packed with ribosome like granules and contained a nuclear apparatus filled with fine nuclear fibrils. Polyphosphate granules also were present in the cytoplasm. The cytoplasmic membrane appeared as a unit membrane invaginated into the cytoplasm and the nuclear region, forming an intracytoplasmic membrane system of complex configuration with lamellar, vesicular or tubular structures. Observations made on negatively stained whole cells revealed that there were no morphological relationships between the membrane system and the reduction site of potassium tellurite.

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1. The culture filtrate of Pseudomonas aeruginosa strain No. 58, which produce only Fluorescence II on glutamic acid liquid medium was fractionated by gel filtration. The crystals of C-substance were obtained from the Fluorescence II fraction.
2. The purified crystals are minute and needle-shaped in form and soluble in alkaline water, alcohol, acetone and ketone. The solution emits an egg yolk-yellow colored fluorescence and possesses the following properties : melting point, 144 C; chemical composition, C₁₇H_23-25O₂ N ; ultraviolet absorption maxima, 210, 256, 346 mμ (in 10^-4 N-NaOH); activation maximum of fluorescence, 360 mμ, and fluorescence maximum, 490 mμ.
3. It is believed that the crystalline C-substance is a part of the aqueous fluorescent substance called pyoverdine.

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Methylene blue which was almost ineffective in the production of respirationdeficient mutants of Saccharomyces cerevisiae suppressed the induction of the same mutants by acriflavine but did not show any effect on the mutation induced by 4-nitroquinoline N-oxide.

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The vegetative cells and sporulating cells of Clostridium tetani and Clostridium bolulinum were examined electron-microscopically by the use of ultrathin sectioning, negative staining, and carbon replica techniques, focusing especially on the observa-tion of the intracytoplasmic membrane system (ICMS). The ICMS which originated from the inward development of the cytoplasmic membrane, could be recognized in the cytoplasm of the vegetative cells of both organisms. The configuration of the ICMS was diverse, exhibiting a multilayered, tubular, vesicular, or reticular ap-pearance. The ICMS was clearly observable in negatively stained whole cell pre-parations, presenting an entire and somewhat stereographical view.
The participation of the ICMS in new septum formation of dividing cells was also recognized. Furthermore, in sporulating cells, it was observed that the forespore membrane was produced by the infolding and the extension of the cytoplasmic membrane into the cytoplasm. The initial spore coat appeared at first fragmentarily in the sporangial cytoplasm surrounding the outer unit membrane layer of the forespore membrane without any appreciable relation with the forespore membrane or the cytoplasmic membrane, and then gradually proceeded to envelope the whole spore portion.
In both negatively stained and carbon replica preparations one to several crescent-or sickle-shaped wrinkles or protrusions on the surface of the cell ends were visible. They were considered to correspond to the marked inner structural changes accom-panying the sporulation and cell division processes.
By observing the carbon replica and chromium-shadowed preparations of cell wall fraction of both organisms, a regularly arranged striped surface pattern with about 125 A or 140 A striation intervals was visible.

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Negatively stained whole cell preparations of Fusobacterium polymorphum were observed electron-microscopically, and a peculiar surface pattern, reminiscent of the surface of the brain, was observed.

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