Review lecture: On the organization of reflecting surfaces in some marine animals

Abstract Reflecting surfaces of fish are formed of stacks of thin, flat crystals composed of guanine, as the m ajor component, and hypoxanthine, as the m inor component. The broad surfaces of these crystals are not, in general, parallel to the surfaces in which they lie in the fish but they are orientated at angles which depend on the function which they serve. T he stacks of crystals in different situations also differ in the num ber and thickness of crystals and in spectral reflectivity. T he organization of these crystals is described, in relation to function, for the silvery surfaces of bony fish, the herring and mackerel, for the reflecting tapeta found in the shark and dogfish, for the photophores of the deep-sea hatchet fish and, finally, for the eye of the scallop.