The ovoviviparons Cyprinodonts are distinguished by a conspicuous sexual dimorphism which has been extensively studied in terms of both genetic and endocrine factors. Hereditary aspects of secondary sex characters have been analyzed in considerable detail in three of these species. Ti1 Xiphophorzcs (Platypoecilus) waculatus and Xiphophorus 7teZZeri Gordon ( '47, '51) and co-workers have demonstrated that the potentialities for most secondary sex characters of each species are present in both sexes and may be manifested hy treatment with the appropriate sex hormone. Winge ( ' 2 7 ) , TTingc and Ditlevseii ('47) and others have found a large series of genes for male coloration which are carried on the 5and Y-chromosomes of Lebistes reticidatus. Haskins and Haskins ( '51) found in several wild populations of Lebistes that some complex and brilliant color patterns behaved as though under the control of single genes, or of a series of very closely linked genes. I n others, patterns were obviously composite and under the control of several genes, iiicluding autosomal genes.
Rather consistent results have been obtained by rarious \-orkei*s in administeriiig sex hormones to Lebistes.