10 cies collected. However, opuntia, Penicillus capitatus and contiguous water and three different sites in 1968. cium in these samples, the total content of organ material and protein nitrogen were also determine From all these data an attempt has been made 1 understand the apparently complex relationshi samples of Halhmeda and Padina gymnospora, sand, were collected at Some analytical data for which govern the concentration of radium, thoriu: these samples are summarized in Table 2. Cajo Margarita (9) and Cabo Rojo (10) are close to each other on the southwest coast and Punta Arenas (12) is on the west coast of the island (Figure 3). From these analytical values, the concentrations of calcium and and uranium by these algae. To this end regressio analysis of the analytical data has been made an correlation coefficients calculated. The values of tt correlation coefficients R, the number of degrees ¢ freedom f and the probability P of there being n radium appear to be lower on the west coast of the island than at the two locations on the southwest correlation in each case are tabulated in Table 3 ac cording to phyta and for the complete sample. In tk case of some of the correlations the values before an after the rejection of suspect data are recorded. coast. Surprisingly, as is shown by the values of the [Ra]/[Ca] ratio, samples of all three species of algae and sand at Punta Arenas concentrate radium preferentially to calcium from sea water by a factor greater than two, while on the southwest coast there 1s, In general, no concentration or even a discrimina- tion. It may be noted further from the values of the [U]/[Ca] ratio there is a discrimination against ura- nium by all of the three species investigated, as well as by sand, at these collection sites. In addition to measuring the concentration of cal- When the degree of calcification imcreases, the prc portion of organic matter in the organism should dc crease. Regression analysis of the analytical data con firms this proposition (Table 3); the correlatio. coefficients of —0.66 (f = 63) for total organic ma terial and —0.69 (f = 67) for protein nitrogen wit] calcium are both highly significant when considerin: all algal samples. Analysis of the data according t: I 0.8 }— O CHLOROPHYCEAE O RHODOPHYCE AE Oo | o >t THORIUM ( jegm/gm} o o | 4 PHAEOPHYCEAE O of 0 | 0.10 0.20 0.30 0.40 CALCIUM (gm/gm) lic. 5.—The variation in the concentration of thorium with the degree of calcification of the algae 15