SUMMARYThe goal of this work was to identify some of the principles underlying chromatophore growth and development in the European cuttlefish, Sepia officinalis. One set of experiments used a regeneration model to follow the re-growth of black chromatophores for 30 days following excision of a small piece of fin tissue. A separate set of experiments tracked and analyzed the addition of new fin chromatophores during a month of normal, undisturbed growth. We also followed the development of individual chromatophores from their initial appearance to full maturation to determine whether their color type was fixed. Based on the results of these studies, we propose five guiding principles for chromatophore growth and maturation.