Section 4. A corporation which limits its membership to the members of a particular fraternal beneficiary corporation, fraternity or religious denomination, or to the graduates of a designated professional or vocational school, or to the employees or ex-employees of cities or towns or of the commonwealth or of the federal government, or to the employees or ex-employees of a designated firm, business house or corporation, or to persons of the same foreign extraction retaining common national interests and designation, and their respective husbands and wives, irrespective of racial extraction, or to persons of the same occupation, may be on the lodge system, and if not on the lodge system, shall be governed by a direct vote of its members without the lodge system. A corporation not so limiting its membership shall be on the lodge system, with a representative form of government, as defined in sections 2 and 3.