The Blood Volumes of Some Representative Molluscs*

The reports of measurements of the blood volume of molluscs found in the literature are few in number and represent, in most cases, incidental observations rather than results of specific investigations. Leitch (1916) obtained by the bleeding of Planorbis a volume of blood which was 33% of the tissue weight. In 1931, Borden determined the blood volume of Planorbis corneus using the Weicker method and obtained a value of 58% of the total tissue weight. This higher value is to be expected, since it is impossible to remove all the blood from an animal by simple bleeding. In 1950, Martin & Huston, using the inulin dilution method, reported the blood volume of Aplysia californicus to be 83·3% of the total weight. This is not surprising since Aplysia has a very extensive haemocoele, and more than half the body weight in blood can be drained in a few minutes from a single incision into the animal.