Conference summary

The black melanin granule of the Brown Leghorn male is a separate particle of complex structure, differing from the brown granules of the female, chick down, and Rhode Island Red. It is feasible to study the granules in the electron microscope directly in the intact feather. MELANIN granules represent an interesting type of separate and character-istic intracellular particle formed by specific cells. While much attention has been devoted to the chemistry of the formation of the pigment, rela-tively little has been directed to the particles themselves, probably because they lie on the border of resolution of the optical microscope. Capacity to secrete these granules may sometimes be lost, but is regained by a mechanism which has some analogies to an infective process. This has been described for grafts of mammalian skin by Billingham and Medawar (1948), and a somewhat similar process may have occurred in the case of human melanoma described by Botha and Lennox (1954). In their case the melanoma metastases, as often happens, had lost the ability to form pigment, but this had been regained whe