Donahue, R.P. (1968) Maturation of the mouse oocyte in vitro. Ph.D. Thesis, Johns Hopkins University. Dunn, H.O., Lein, D.H. and Kenney, R.M. (1968) XX/XY chimerism in a bovine true hermaphrodite: an insight into the understanding of freemartinism. Cytogenetics. In press. Fechheimer, N.S., Herschler, M.S. and Gilmore, L.O., (1963) Sex chromosome mosaicism in unlike cattle twins. In Genetics Today, Ed. S.J. Geerts, MacMillan & Co., New York. Ferguson-Smith, M.A. (1966) X-Y chromosomal interchange in the aetiology of true hermaphroditism and of XX Klinefelter's syndrome. Lancet ii: 475-476. Gartler, S.M., Waxman, S.H. and Giblett, E., (1962) An XX/XY human hermaphrodite resulting from double fertiliza- tion. . Proc. Nat. Acad. Sci., U.S., .48: 332-335. Gerneke, W.H. (1964) The karyotype of a gonadal male pig inter- sex, &5, Africids SciĀ„ 60:347=852, Gerneke, W.H. (1965) Chromosomal evidence of the freemartin condition in sheep - Ovis aries. J. S. Afriq. Vet. Med. Ass. 36: 99-104. Gerneke, W.H. (1967) Cytogenetic investigations on normal and malformed animals, with special reference to inter- sexes. Onderstepoort J. Vet. Res. 34: 219-300. Goodfellow, S.A., Strong, S.J. and Steward, J.S.S. (1965) Bovine freemartins and true hermaphroditism. Lancet i: 1040-1041. 864