Particular interest is attached to cutaneous tumors of fishes because of the variety of pigment cells from which such growths may have their origin. The pigmented cells of the corium of fishes are usually grouped as melanophores, xanthophores, erythrophores, and guanophores or iridocytes. The normal morphology of these cells has been extensively studied by many investigators, including Ballowitz (1), Becher (2), Schnackenbeck (3), Jost (4), Panu (5), Graupner and Fischer (6). Pigmented tumors of fishes are not uncommon. Of these, the variety most frequently seen is the melanotic type studied by Takahashi (7), Thomas (8), Johnstone (9), Haddow and Blake (10), and others. In this connection it is noteworthy that Haüssler (11), Kosswig (12), and Gordon and Reed (13) have encountered melanotic invasive growths experimentally in hybrids of the Mexican killifish. A tumor containing yellow green pigment together with crystals (allophor sarcoma) is described by Takahashi (7). The same author found another iridescent tumor called guanophoroma in a specimen of <i>Hexogramm otakii.</i> Through his studies information regarding the physical characteristics of crystals in fish tumors has been gained. To date only a few red pigmented fish tumors have been studied. Thomas (8) has described three specimens designated by him as erythrophoroma, all in fishes inhabiting European waters. The first of these, in a tunny, was a subperitoneal tumor near the esophagus, of a mandarin color, with a metastatic nodule in the liver. The other two were in specimens of trout, metastasis occurring in one of these.