The plankton samples were sorted under a dissecting microscope equipped with polarizing filters. The filters were placed between the sample and the light source, and between the sample and the microscope lens. The filters were rotated until the shells of bivalves and gastropods appeared to ‘glow’ due to the birefringence caused by the crystalline structure of the shell (Gallager
et al. 1989). Lighting the samples in this way greatly facilitated sorting. Bivalve larvae were identified to genus and, when possible, to species using various identification guides (Thorson 1946, Sullivan 1948, Rees 1950, Loosanoff et al. 1966, Chanley & Andrews 1971). During the processing of the physical oceanographic data, current velocities were decomposed into alongshore and cross-shore components. Alongshore was defined as 20°W of true north. Contour plots of the distribution of the biological and physical data were made using the Noesys Transform contour plotting program with the Kriging option for gridding and interpolating. In these plots, the position of contours close to shore (within 5 km), because of the short distance between stations, are accurately depicted. As station spacing increased with distance offshore, the degree of confidence with which we viewed the position of contours decreased. If larvae are acting as passive particles, then they should follow a water mass as it is displaced and the concentration of the larvae should be correlated to the physical parameters defining the water mass. If the larvae are not acting as passive particles, then significant correlations with the physical parameters should not be present. Spearman’s Rank correlations between the concentration of the larval taxa and distance from shore,