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Microscopic and macroscopic views of the bovine embryo. Microscopic and macroscopic views of the bovine embryo during the elongation phase: spherical (S), ovoid (O), tubular (T) and filamentous (F) shapes appear sequentially from Day 9 (S) to Day 12–13 (O), Day 14–15 (T), and Day 16–18 (F). All these steps precede the onset of implantation (D19-21).
