SYNOPSIS The pigmentation of poikilotherms is based upon the presence of deimal chiomatophoies melanophores, lndophores, and xanthophores The form function, and composition of each chromatophore type is discussed, and variations n melano some composition are described Recent theories about the mechanism of melanosome movement are discussed The role of mdophores in pigmentation processes is described and their impoitance in structural coloration is evaluated Interrelationships of the pigmentary organelles of all three chromatophores are discussed, and evidence is piesented that they have a common origin Associations of pigment cells with themselves or with other elements of the integument are described as i basis for chromatophore function