1. Myxine glutinosa responds to illumination by active locomotory movements.
2. The response to light occurs some time after the onset of illumination. This time can be resolved, after the method of Hecht, into a sensitization period and a latent period.
3. Analysis of the relation of sensitization period and latent period to intensity of illumination and other factors shows that photoreception in Myxine is essentially similar to that of a number of other animals, including the ammocoete, but suggests that the secondary reactions initiated by the production of photolytes during sensitization occur during both sensitization and latent periods and not during the latent period alone.
4. The photoreceptors of Myxine are located in the skin and are present only, or mostly, at the anterior end of the head and in the region of the cloaca. Nervous impulses travel from the posterior photoreceptors through spinal nerves to the spinal cord.