The role of the centrosome in microtubule dynamics, as many other central problems of modern cell biology, was inspired by the work of Keith Porter. One particular system that he introduced to experimental analysis was the fish melanophore. This cell, residing in the pigmented skin of fish or amphibia, contains many thousands of granules of pigment and is a device of nature by which prey attempt to evade their predators. When stimulated by the hormone, adrenalin, the pigment granules of the melanophore aggregate to the center of the cell, reducing the cell's optical density and thus lightening the color of the skin tissue. The melanophore can also disperse its pigment, restoring the darker coloration. Excellent reviews of the biology of melanophores and their contribution to our understanding of intracellular transport mechanisms have been written by Schliwa (Schliwa and Euteneuer, 1983; Schliwa, 1984) who began his studies of this system independently in Munich but for several years was an investigator in Porter's department in Boulder, Colorado.
