radioactivity in the samples is often limited to isolated areas or "specks", most of which are assumed to be fallout particles. The term "speck" contamination is used to denote spotty activity on organisms, presumably caused from insoluble radioisotopes. The identification and distribution of "specks" in sand, plankton, algae, invertebrates, fish and land plants are discussed below. Sand. An autographic technique found useful for locating these radioactive particles involved spreading sand on scotch tape, inverting to remove loose particles, and exposing with firm contact against fast film. After developing, a positive transparency was printed on the film to be placed beneath the sand sample so that when in perfect registry the radioactive particles would be illuminated if viewed by transmitted light. Engebi beach sand showed spots that were associated appar- ently with only the finer sand particles. Some of the active particles were isolated by successive dichotomous division of a sample of sand and retention of the more active half, as de. termined by the end window survey meter, until the individual particles which contribute most of the radioactivity could be picked out under the microscope. In Figure 17 sand samples and active and non-active particles which have been separated from the samples are shown. Counting rates for the particles are given in the legend for the same figure. In Biijiri dredged sand radioactive particles were different in appearance from inactive particles. - 86 - Active particles