external ovular transmigrationdirect ovular transmigrationinternal ovular transmigrationindirect ovular transmigration the passage of an ovum from one ovary into the fallopian tube of the other side; external ovular transmigration, direct ovular transmigration occurs when the ovum passes across the pelvic cavity; internal ovular transmigration, indirect ovular transmigration occurs when the ovum crosses the uterine cavity and so enters the tube of the opposite side.