.m~zm~ ~o~s 221

While Amoeba proteus has long been the subject of extensive cytological and cytochemical studies, investigations with the electron microscope have been limited principally to the nuclear membrane (1-3). The observations reported herein were made in the course of studies intended to correlate cytochemistry (4) with knowledge of fine structure obtained with the electron microscope. I t is felt that the unique character of these observations justifies this brief note, The amebas were first washed free of other protozoa, and then fixed with 1 per cent OsO4 in a veronal-acetate buffer~ pH 8.6, containing 0.01 per cent CaCI~. Fixation time varied from 10 to 20 minutes. After dehydration :and embedding in n-butyl methacrylate, thin sections were cut and subsequently studied in the electron microscope (RCA, EMU-2E). The characteristic nuclear structure is seen in Fig. 1. Just within the unusually thick and complex nuclear membrane (NM) are numerous dense bodies (D) which range from 0.4 to 1.7 g in size. Such bodies, as described by Chalkley (5), stain intensely with hematoxylin but are Feulgen-negative. The more interior regions of the nucleus, beyond these peripheral bodies, show a diffusely Feulgen-positive reaction. In these regions, we have found clumps of helical structures. These helices are single and not paired. I t is difficult to trace their origins. The longest spirals are between 2500 and 3000 A in length and radiate irregularly from a diffuse central region