The Color Changes in Uca Pugilator

During recent years it has been proved, especially through the investi- gations of Koller and of Perkins, that there probably is an organ in the eye-stalks of crustaceans, which by incretory means controls the color changes of the body.This organ is influenced by stimulations from the eyes.The incretory substance is similar to a hormone and brings about contraction of the chromatophores in Crangon and Palaemonetes.Kropp and Perkins (1933) have found that this hormone occurs in the eye-stalks of all crustaceans thus far investigated, some 16 species, even in those in which there are no color changes themselves.Meyer (1931) showed that this hormone is not only active in the chromatophores of crustaceans but also calls forth contraction of the color cells in fishes (Gobius and Pleuronectes).In 1933 Kropp and Perkins proved that an injection of extract from the eye-stalks of crustaceans into tadpoles of Rana clamitans brings about a strong expansion of the chromatophores in this species. Koller states (1928) that in Crangon he has succeeded in getting expansion