X chromosome
(biology 生) chromosome that occurs as one of an identical pair in female cells to produce a female in the reproductive process, or singly combined with a single Y chromosome in male cells to produce a male X染色体. Cf 参看 Y chromosome (Y).
Our knowledge of the oceans a hundred years ago was confined to the two-dimensional shape of the sea surface and the hazards of navigation presented by the irregularities in depth of the shallow water close to the land.