Heterosexual Cells in Testes of Chimeric Marmoset Monkeys

Abstract

The testes of three marmoset monkeys in whom a percentage of marrow cells was found to be derived from a female co-twin were studied. In two of the animals some XX mitoses of presumed spermatogonial origin were present. After delineation of the XY bivalent in first meiotic metaphases, some cells were found in two animals in which no XY bivalent could be identified. These findings are interpreted to support the suggestion by Ohno <i>et al</i>. (1962), that germ cells occasionally reach the circulation of mammalian embryos and may be distributed to the gonads of co-twins.