The Raman spectrum of a cell homogenate obtained from the unfractioned blood cells of Ascidia gemmata was recorded in an effort to determine the ratio of the level of sulphate to that of vanadium in the blood cells. The ratio obtained was 1·47, which is close to 1·5, the value predicted if sulphate ions are present as the counter ions of V3+ ions. We found evidence that an aliphatic sulphonic acid is present in the blood cells, namely, the Raman spectrum of the cell homogenate included a band at 1044 cm−1, which corresponds to the symmetrical stretching vibration of the SO3− group of the anion of cysteic acid.