HORMONAL CONTROL OF ALL PIGMENTS
Since the work of Roller ('27) on Crangon vulgaris, in which he was able to get a distinct reaction of the chromatophores of these animals by blood transfusion, it has been suspected that all chromatophores were under the control of humoral substances carried in the blood. This view was strengthened by the fact that no one had been able to demonstrate nerve endings in the chromatophores of the animals. Perkins ('28), working upon Palaemonetes with special reference to the red and yellow pigments, confirmed the idea of humoral control for these two pigments by demonstrating that they no longer reacted to backgrounds when the blood supply to the chromatophores in question was interrupted. Furthermore, nothing that he could do in the way of severing nerves supplying certain regions of the body had any effect upon responses of the red and yellow pigments of those parts. The little doubt of such a hormonal control that remained was finally swept away when Perkins showed that a substance was located in the eyestalks of the animals which when injected into the blood would bring about a concentration of the red and yellow pigments. 'To Dr. G. H. Parker, under whose guidance this research was conducted, I am greatly indebted for many generous suggestions and much constructive criticism.