Abstract
1. The survival of Artemia salina adults in various media has been studied. 2. Prolonged survival is only possible in media in which certain sodium salts (principally NaCl) predominate. 3. Certain substances are found to be highly toxic. 4. It is confirmed that the high toxicity of potassium ions can be antagonized by sodium ions. 5. The results indicate that the animal is appreciably permeable.