The Reactions of Chromatophores as Evidence for Neurohumors

Chromatophores are one of the six or seven kinds of effectors found in animals. Unlike muscles and glands, which are almost universal in their occurrence, chromatophores are much limited in distribution. With the exception of a few sporadic cases such as the leech (Janzen, 1932; Wells, 1932) and possibly certain sea-urchins (von Ueküll, 1896) the animals that exhibit color changes due to chromatophores are the mollusks especially the cephalopods, the arthropods particularly the crustaceans, and the lower vertebrates. The chromatophores in these three groups of animals have without doubt originated independently, as the striking differences in their organization show.