Until recently only the uppermost layers of marine sediments have been generally available for scientific investigations since most coring instruments obtained samples less than a meter long. The early bacteriological investigations of Certes (1884), Russell (1892), Fischer (1894), Gazert (1912), and Drew (1912) were confined to surface samples obtained by dredging. Lloyd (1931) was the first to report quantitative data on the vertical distribution of bacteria in subsurface layers of marine sediments. Similar investigations were made by Reuszer (1933), and Waksman et al. (1933) .