Centriole formation in male meiosis of the hyrax, Heterohyrax syriacus, and the Berdmore palm squirrel, Memetes berdmorei, was investigated by serial section analysis of selected regions of the seminiferous epithelium and isolated meiotic cells. Two periods of centriole formation were observed, a first in cells in transition between zygotene and pachytene and a second in the secondary spermatocytes. The duplication events before each meiotic division insured the presence of a centriolar duplex at each division pole. The parental member of each duplex of the second division was closely associated, at its distal end, with the plasma membrane. This orientation was established in the secondary spermatocyte and persisted until the completion of telophase II. Subsequently in early spermatids, each duplex assumed a characteristic orientation adjacent to the nucleus.

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