Section 4. In each planning district so established there shall be a district planning commission consisting of one member of the planning board of each city and town voting to join such district, elected annually by said planning board and certified in writing to the district planning commission. Said member may be replaced by a two thirds vote of his planning board before the termination of his annual appointment. In the case of the planning board’s failure to elect a delegate in any year the previously named delegate shall continue to serve until his successor is qualified, as long as he shall remain a member of his local planning board. There may be an alternate designee, who may or may not be a planning board member, who shall be a resident of the city or town he represents, appointed annually and certified in writing to the district planning commission by the mayor in a city, confirmed by the council, or in the case of a city with a plan E form of government, appointed annually by the city manager, or in a town by the selectmen or in towns with a manager form of government, by the town manager, who may attend meetings of the district planning commission and who shall assume the rights and duties of the planning board member in his absence. The alternate designee shall be named in writing to the district planning commission annually in order that he may perform the duties and exercise the powers authorized in this section. In a member town which has not established a planning board, the selectmen shall annually appoint a member of the district planning commission. Such district planning commission shall annually elect a chairman, a vice chairman, a treasurer, and a clerk from among its members and alternate designees, and may elect an assistant clerk, from among such members and alternate designees. The treasurer and assistant treasurer shall give the commission a bond, with a surety company authorized to transact business in the commonwealth as surety, for the faithful performance of their duties in such sums and upon such conditions as the commission may require. The said commission may employ experts and clerical and other assistants. All meetings of the commission shall be held at the call of the chairman and at such other times as the commission may determine. A quorum of the commission shall consist of at least one fourth of the duly named members or alternate designees. Lack of a quorum shall not prevent the members at an officially called meeting from coming to order, making motions, discussing or passing a motion to continue said meeting to a later time. The commission shall establish rules of procedure for its activities and shall keep a record of its meetings, transactions, resolutions, findings and determinations, all of which shall be public records.