Sunlight exposure is strongly indicated as one of the important etiologic agents in human cutaneous malignant melanoma. However, because of the absence of good animal models, it has not been possible to estimate the wavelengths or wavelength regions involved. We have developed a useful animal model from crosses and backcrosses of platyfish (Xiphophorus maculatus) and swordtails (Xiphophorus hel...

A sex-linked gene, P, controls the onset of sexual maturity in the platyfish, Xiphophorus maculatus. The activity of this gene is correlated with the age and size at which the gonadotropic zone of the adenohypophysis differentiates and becomes physiologically active. Immature fish of all genotypes grow at the same rate; however, as adults, males with "early" genotypes are significantly smaller ...

Received for publication October 2, 1954. intestine. These findings, which appear to imply an extraordinary mobility of thyroid tissue in normal and goitrous fish, are presented for both their in trinsic interest and their possible value in the in terpretation of atypically located thyroid tissue in man. When first noted in a number of genetic strains of the platyfish (Xiphophorus mactdatus), h...

To determine the nutritional requirment for iron in fish growth, the effect of daily addition of supplemental ferrous sulfate on the growth of Xiphophorus helleri and Xiphophorus maculatus (the swordtail and the platyfish) was measured by determination of weight gain and hematocrit levels. Both variables increased as a result of the added iron. The effectiveness of the treatment diminished as s...

presence of thyroidal tissues in places in the body far removed from the usual pharyngeal em bryonic source has often stimulated considerable speculation and discussion. For example, thyroidal follicles in the human ovary (struma ovarii) are believed by Means (5) to be local teratomatous tis sues, and not metastatic growths, benign or other TABLE 1 p Plus sign indicates that tumors are present ...