THE ACTION OF EYE-STALK EXTRACTS ON RETINAL PIGMENT MIGRATION IN THE CRAYFISH, CAMBARUS BARTONI

¹ From the Biological Laboratories, Harvard University

A substance similar to, or identical with, the eye-stalk or chromatophorotropic hormone may be obtained from the eye-stalks of crayfishes. When injected, in proper amount, into light-adapted crayfishes it causes the distal and proximal pigments to migrate to more extreme "light positions" than normal. When injected into dark-adapted crayfishes which are allowed to remain in the dark it causes the migration of one or both sets of screening pigment to their "light positions." The distal pigment has a lower threshold than the proximal pigment, as it is affected by lower concentrations of the active substance. It is suggested that such threshold differences may account, in part, for the unusual pigment responses which have been observed in compound eyes in studies of 24-hour cycles in pigment migration.