SUMMARY : During normal movement most motile bacteria carry a straight tail, which, when the movement slows, stiffens into helical structures commonly called flagella. The helices of many kinds of bacteria were photographed with a sunlight darkground microscope, and their wavelengths measured. Mean values and standard deviations were calculated for eacli strain and then for the species. 'Biplicity' (two wavelengths per bacterium, one twice the other) was observed frequently. Each strain appears to have its own constant wavelengths. The wavelength differs in different kinds of bacteria from 0.60 to 5058p., the distribution over the various species not revealing a distinct pattern nor any obvious correlation with other characteristics. The wavelength is affected by temperature, pH value, and colloid content of medium. These features, and the effects of drying, make stained preparations useless for measuring.

Fine dendritic crystals loaded at their ends with hemoglobin were found to be growing at the evaporating edges of an open hanging-drop preparation of blood diluted with normal saline. In another area dendritic crystals were growing direct from red cells. This phenomenon was found to be reproducible, as also the growth of larger crystals made with stronger NaCl solutions. These structures were identified as atypical NaCl crystals. Large as well as fine dendritic crystals were found still to form after removal of the red cell membranes and stroma and after the removal of plasma together with the remnants of hemolyzed red cells. It was concluded that hemoglobin was the sole agent responsible for modifying the form of the NaCl crystals. It was further apparent that NaCl has a strong affinity even for intracellular hemoglobin, and that hypertonic saline hemolysis of red cells can take place without any shrivelling of the cell membrane, occurring at the site of "membrane defects" located on the cell surface.