Abstract
1. The results of some chemical analyses for inorganic and organic constituents of the seminal plasma of Balanus balanus are presented. 2. The inorganic ions show a cation deficit of 178 m-equiv./l., which is probably made up by free amino-acids. 3. Cystine is a prominent amino acid present. 4. Potassium and calcium are present in excess of their quantities in sea water. 5. Reducing sugars, compared with the amount found in sea-urchin spermatozoa, are found in moderate quantities, 1 mg./ml. 6. Phosphorus of all kinds is present in only small quantities (total of o.14 mg./ml.). 7. Some phosphatases are present. 8. There are 21 /µg./ml. of ascorbic acid; the function of this is discussed in relation to its possible contribution to the protective action against the poisoning of -SH groups by thiol-reactive agents.