THE CHROMATOPHORE SYSTEM IN THE CATFISH AMEIURUS

¹ From the Biological Laboratories, Harvard University

1. The melanophore system in the catfish Ameiurus composed of epidermal micromelanophores and of subdermal macromelanophores is activated not through direct stimulation by light, by humors from the eye ball, nor by the activity of the pineal organ, but by nerve impulses received from the eyes and from the photoreceptors in the skin.

2. The skin photoreceptors are stimulated by light but not by darkness and are exclusively concerned with the discharge of intermedin from the pituitary gland whereby the catfish darkens (neuro-humoral reflex).

3. The eyes are differently stimulated by light from a black environment and by light from a white one. In the former they give rise to impulses that pass over the dispersing autonomic nerve-fibers, induce a discharge of acetylcholine, the dispersion of pigment, and the darkening of the fish. In the latter they originate impulses that pass over the concentrating autonomic fibers, induce a discharge of adrenaline, the concentration of pigment, and the blanching of the fish. Impulses induced through the eye by an illuminated, white environment probably also inhibit the discharge of intermedin from the pituitary gland.

4. A technique is described for the transection of the catfish brain at the level of the cerebellum whereby the eyes and their appended centers may be separated from the whole integumentary photoreceptor system and its centers.