1. The normal paradise fish adapts itself by appropriate color changes to environments of black, white, red, yellow, and blue. 2. Analogous but less adaptive changes occur in the albino. 3. The reactions of melanophores, xanthophores and erythrophores which produce these color changes are described. 4. Dark caudal bands, formed by cutting chromatophore nerves in the caudal fin of normal paradise fish fade in approximately ten hours. Similar bands in the albino fish fade in about four hours. 5. The evidence indicates the presence of independent dispersing neurohumors for melanophores and for erythrophores. 6. The rate of caudal band disappearance is directly proportional to the temperature, and a rise of about ten degrees in temperature very nearly doubles this rate.