Section 3. Subject to the approval of the governor and council, the commissioner may appoint and remove a deputy commissioner, and a deputy commissioner and general counsel. In case of a vacancy in the office of the commissioner, and during his absence or disability, the deputy commissioner shall exercise and perform the powers and duties of the office of commissioner. In case of the absence or disability of the commissioner and the deputy commissioner, the deputy commissioner and general counsel shall exercise and perform the powers and duties of the office of commissioner. The commissioner may appoint and remove such assistants as the work of the division may require. He shall be allowed necessary expenses, including those for the investigation of, and prosecution for, violation of any provision of sections ninety-six to one hundred and fourteen, inclusive, of chapter one hundred and forty, and the actual expenses incurred by him and his subordinates in traveling in the performance of official duties. The assistants shall give bonds, with sureties to be approved by the commissioner, for the faithful performance of their duties.