Abstract
Spectral sensitivity and dark-adaptation in Mysis relicta were studied by a behavioral method. The mysid eye has 1 peak of sensitivity to light at a wave length of approximately 515 u and another at or below 395 u. Dark-adaptation progresses rapidly. Mysids responded to a light intensity of 9 x 10-6 foot-candles after 9 minutes and 45 seconds in the dark. A study of phototaxis showed that their response depended on the immediately previous experience (length of time in light or dark). The mysids responded photopositively unless they had been in total darkness at least 10 hours; then they responded photo -negatively.