Mass. Gen. Laws ch. 18 § 4
The commissioner shall appoint a deputy commissioner and such assistant commissioners, not to exceed four in number, as the commissioner may determine to be necessary or desirable to carry out the work of the department. The deputy and assistant commissioners shall be assigned areas of responsibility to be specified by the commissioner. At the time of appointment the deputy commissioner and each such assistant commissioner shall possess qualifications of training and experience generally similar to those required of the commissioner or otherwise suitably preparing him for the work of his office. The position of deputy commissioner shall be classified in accordance with section forty-five of chapter thirty and the salary shall be determined in accordance with section forty-six C of said chapter thirty. The positions of assistant commissioner shall be classified in accordance with section forty-five of chapter thirty and the salary shall be determined in accordance with section forty-six C of said chapter thirty.
The deputy commissioner and the assistant commissioners shall devote their full time during business hours to the duties of their respective offices. If the office of the commissioner becomes vacant, the deputy commissioner shall discharge the duties and have the powers of the commissioner. During the absence or disability of the commissioner, the deputy commissioner shall discharge the duties and have the powers of the commissioner; and, if the office of the deputy commissioner is vacant or if the deputy commissioner is absent or disabled at the same time as the commissioner, an assistant commissioner designated by the commissioner shall discharge the duties and have the powers of the commissioner. The deputy commissioner and each assistant commissioner shall give a bond to the state treasurer for the faithful performance of his duties in such sum as the comptroller may prescribe.
Mass. Gen. Laws ch. 18, § 4