. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ACTIVE HOLOTHURIAN MOVEMENTS 111 of the area on the Caribbean Sea, in the lee of the heavy swells and surf action of the Atlantic coast of Puerto Rico. Sediment analyses reported by Guillou and Glass (1957) confirm the divergent character of the substrata as revealed in the present study. Calcareous and non-calcareous materials were observed to be present in equal amounts in the beach sands from Aguadilla to Rio Camuy, while inshore sediments along the southwestern coast (all of south coast as shown in Figure 2) were predomi
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ACTIVE HOLOTHURIAN MOVEMENTS 111 of the area on the Caribbean Sea, in the lee of the heavy swells and surf action of the Atlantic coast of Puerto Rico. Sediment analyses reported by Guillou and Glass (1957) confirm the divergent character of the substrata as revealed in the present study. Calcareous and non-calcareous materials were observed to be present in equal amounts in the beach sands from Aguadilla to Rio Camuy, while inshore sediments along the southwestern coast (all of south coast as shown in Figure 2) were predominantly calcareous. 99 99 2 95 • : 84 ^ I 50 16 5. 0 - Crasnboat Landing Terrigenous residue Calcium carbonate Organic matter 368 b - Cayo Caracoles trace Phi-units and grain size mm FIGURE 3. Plot on probability paper showing cumulative percent distributions of grain size in sediment samples from Astichopus habitats at Crashboat Landing, Aguadilla (a) and Cayo Caracoles, La Parguera (b). The per cent composition of the samples, based on dry weight, is tabulated in terms of terrigenous residue, calcium carbonate and organic matter con- tent. Grain size distribution was determined by standard sieve analysis, calcium carbonate and organic matter contents by the difference in weights obtained after ample treatment with HC1 and H2O2, respectively. The H2C>2 technique employed is outlined by Stevenson and Emery (1958). Terrigenous residue, as here denned, was that portion of the sample remaining after the above treatment. Movements Clark (1933) observed that Astichopus is a very active form and remarked (p. Ill) that it ". . moved about more obviously than any other large holo- thurian I have ever ; The various movements performed by Astichopus were studied in the field during daylight hours and in the laboratory during the day and at night. Animals maintained in captivity were kept in 200-liter DUROTEX (as
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