1. Oxyhaemoglobin dissociation curves have been obtained for Glossoscolex giganteus. The t50 value was 7 mm. Hg. at 20° C. and pH 7.58. There was no significant Bohr effect.

2. Oxygen capacity averaged 14.0 vol. % for fifteen animals. The corresponding value for haemoglobin expressed as iron content was 30 mg. %.

3. Blood was sampled anaerobically from the dorsal vessel on non-anaesthetized freely moving specimens and analysed for O2 and CO2 content. Blood-gas levels were studied in animals placed on moist surfaces or buried in shallow moist soil. The effects of drug injections and changes in the composition of the external gases were measured.

4. Patterns of gas exchange and the role of haemoglobin in gas transport in the earthworm are discussed.

This work was supported in part by Grant GB-358 of the National Science Foundation, by grant HE-02557 of the National Heart Institute, and by a travel grant of the Fulbright Commission to the junior author.