ABSTRACT
That the effectively eyeless hag, Myxine glutinosa, is responsive to light was reported by Gustafson (1935). Our own interest was aroused by the behaviour of some hags (kindly sent to us by Dr Gustafson) which were being photographed. A tank containing a number of them was brightly illuminated for a few seconds only. Some 20 sec. later the animals, which had previously lain motionless in the semi-darkness, started, rather suddenly, to swim. The long delay between stimulus and response seemed to merit study while the definiteness of the response promised an important help to observation. The present paper reports the behaviour of hags under different conditions of illumination and a preliminary investigation of the sensory physiology of their responses.
