Members of the Senate and General Assembly shall receive annually, during the term for which they shall have been elected and while they shall hold their office, such compensation as shall, from time to time, be fixed by law and no other allowance or emolument, directly or indirectly, for any purpose whatever. The President of the Senate and the Speaker of the General Assembly, each by virtue of his office, shall receive an additional allowance, equal to one-third of his compensation as a member.