A miscegen is a hybrid, particularly of white and black.
1864. Miscegenation occurs as the title of a pamphlet. (N.E.D.)
1864. A very sprightly suffragan of a miscegen stamp . The result would be an average miscegen and a superior patriot.S. S. Cox, Eight Years in Congress, p. 354 (1865).
1864. [Do they] rely upon the new system, called by the transcendental abolitionists Miscegenation, to save the black?Id., p. 357.
[See the whole speech, pp. 35270.]