Any casual vacancy in the office of an elected Commissioner or of a Commissioner appointed by name caused by the death or resignation of such Commissioner or by virtue of the provisions of sub-section (2) of section 17, shall be filled within one month by election or appointment, as the case may be, in the manner hereinbefore provided:Provided that the Commissioner so elected or appointed shall retain his office so long only as the vacating Commissioner would have retained the same if such vacancy had not occurred.
