The aim of this thesis is to investigate the peripheral organization of the chromatophore system of Eledone cirrhosa at the level of the chromatic and physiological units.The structure of the chromatic elements is investigatedwith light and electron-microscopy. The structure of the leucophores and iridophores of E. cirrhosa is similar to thestatic elements of other octcpods. The leucophores consistof a central cell body bearing ovoid electron-dense protrusions (leucosomes). The iridophores are made of a central cell body surrounded by stacks of electron-dense discoidal platelets(iridosomes). The chromatophores are true organs made of a central cell containing the pigment granules, surrounded by fifteen to twenty radially arranged muscle fibers. The contraction of the muscles produces expansion of the pigmentcell. The radial muscles are of the obliquely striated type. They differ from those of squids in that the contractile filaments occupy the core of the fiber and they contain fewer mitochondriae. Most of the chromatophore muscles are innervated in an "en passant" fashion by thin varicose axons whichcontact some of the muscles of several chromatophores. The f chromatic units represent morphological groupings of the three elements.The innervation of the chromatophore muscles investigated with cobalt filling or stimulation of nerve bundles in the skin with suction electrodes. The chromatophores forming a motor unit are dispersed over several chromatic units and probablyrepresent parts of particular patterns. There is evidence that variations of the stimulus frequency modifies the numberof chromatophores triggered by a single axon. It is thus suggested that recruitment of motor units is responsible for the different patterns seen in vivo while recruitment through frequency could account for the intensity with which these patterns are expressed.