No abstract

1. Individuals of Cryptochiton stelleri, as representatives of the class Placophora, distributed inulin in blood volumes yielding a mean of 43.8% of the wet body weight without shell. Mean cellular water was estimated to be 76%. 2. The two opisthobranch gastropods examined were found to have very large mean blood volumes. Aplysia californicus distributed haemoglobin in 76.2% and mild silver proteinate in 73.1% of the wet body weight. Inulin was distributed in a significantly larger space averaging 79.3% of the body weight, which probably included pericardial and renal spaces. Archidoris sp. distributed inulin in 65.4% of the wet body weight. Mean cellular waters were 74-79% in Aplysia and 83% in Archidoris. 3. Two pulmonate gastropods were studied with inulin which was distributed in a mean space 40.3% of the wet body weight without shell of Achatina fulica, and 36.6% of the wet body weight in Arion ater. The computed cellular waters were 77 and 79%, respectively. 4. Excellent agreement was shown between a marine pelecypod, Mytilus californianus, and a fresh-water pelecypod, Margaritana margaritifera, of similar body size and form. Inulin in the former was distributed in 50.8%, and in the latter inulin and T-1824 in 49% of the wet body weight without shell. The cellular water contents were 80 and 76%, respectively. 5. In a single representative of the Cephalopoda--Octopus hongkongensis, it was possible to demonstrate with T-1824 and with HgS a blood volume averaging 5.8% of the wet body weight, constituting a fluid space distinctly different from the tissue fluid space. Inulin was distributed in the entire extracellular space amounting to 28% of the wet body weight. The cell water which was calculated from the mean values obtained was 77%.