An Act amending the act of April 29, 1937 (P. L. 487, No. 115), entitled, as amended, "An act to provide for the permanent personal registration of electors in cities of the second class, cities of the second class A, cities of the third class, boroughs, towns, and townships as a condition of their right to vote at elections and primaries, and their enrollment as members of political parties as a further condition of their right to vote at primaries; prescribing certain procedure for the conduct of elections and primaries and the challenge and proof of qualifications of electors; requiring the county commissioners of the various counties to act as a registration commission therefor; and prescribing the powers and duties of citizens, parties, political bodies, registration commissions, commissioners, registrars, inspectors of registration and other appointees of registration commissions, county election boards, election officers, municipal officers, departments and bureaus, police officers, courts, judges, prothonotaries, sheriffs, county controllers, registrars of vital statistics, certain public utility corporations, real estate brokers, rental agents, and boards of school directors; and imposing penalties," authorizing change of registration by mail.