Abstract
1. No reversible oxygen-binding by the blood of the tunicate
A. nigra is detectable.
2. Blood cells contain iron(II) and vanadium(III), and a yellow-green chromogen which can be separated from the metals by fractionation on Sephadex G-100.
3. The chromogen will reduce oxygen in alkaline medium, it is heat-stable and has absorption peaks at 280 and 330 nm (in 0.1 N HCl). The peak at 330 nm is lost on oxidation.