Fig. 5. Comparison of movement of various water-soluble materials across the escutcheon region of the proximal end of 0-1-week-old oothecae using microparabiotic chambers (Figs 1, 4). Comparisons of the rate of isotope movement from the exterior side to the interior side of the oothecal surface were measured using 1 µl samples taken at 0.5 h, 2 h, 6 h and 24 h incubation times. Radioactivity recovered on the inside of the oothecal covering is reported as log% of the initial radiolabel placed on the exterior side of the covering. Molecular weights (Da) of the isotopes used are shown in parentheses. The number of replications (N) used for data analysis is shown for each material. Statistical comparisons of the means were done using ANCOVA (analysis of covariance); different letters associated with the curves indicate significant differences at the P=0.05 level.