The terms of office of two members of the first civil service commission shall be one year. The terms of office of the other members of the first commission shall be two, three, and four years, respectively. If the commission is composed of seven members, the terms of office of all members of the first seven-member commission shall be fixed by lot at one year for two members, two years for two members, three years for two members, and four years for one member. The members shall determine by lot the relative order of the expiration of their terms.