Colony Organization of Certain Bacteria with Reference to Sporulation.

Accounts of the study of colonial organization of bacteria and other microorganisms by means of thin sections have appeared sporadically in the literature for nearly fifty years. Neisser in 1888 devised a procedure for obtaining individual sections of colonies grown in gelatin or agar shake cultures. The plugs of medium were removed from the culture tubes by gentle warming, cleared in a 1 per cent aqueous solution of potassium bichromate, washed, and carried through a graded series of alcohols into 95 per cent alcohol. The plugs were cut into blocks with one colony in each. The blocks were then mounted on pieces of cork, with gum arabic, and placed in absolute alcohol for 24 hours. By means of a sliding microtome, sections were cut, mounted on slides with fixative, stained, and cleared in the usual manner. Neisser's paper is confined to a description of the technique alone, but is of interest since it is apparently the first comprehensive report of a method for sectioning colonies of microorganisms. Hutchinson in 1907 studied sections of surface and subsurface colonies of Bacillus subtilis, Bacillus megatherium, Saccharomyces cerevisiae, "Mycoderma" cerevisiae, and Oidium lactis. In the case of surface colonies, he poured lukewarm melted agar containing 3 per cent formalin over the colonies, and, when the agar hardened, removed the colonies intact. The colonies were then imbedded in paraffin and sectioned. In the bacterial colonies he found the cells at the margin to be of normal size and ap-