Section 6. It Shall Be Proper for Said Cities to Provide, by Ordinance,

for the exercise of all rights and powers herein conferred upon the City Planning Commission, by a park commission, or kindred municipal bureau or commission, authorized under existing laws. And no person holding office under the government of any of said cities, except the mayor, members of councils, or commissioners, shall be ineligible to serve as a member of a City Planning Commission.