In the case of consolidation of two or more cities, under the laws of the commonwealth, the boards of registration commissioners of said cities, provided for and appointed in accordance with an act, entitled “An act to provide for the personal registration of electors in cities of the first and second classes of this commonwealth to make such registration a condition of the right to vote in such cities, and to provide penalties for the violations of its provisions,” approved the seventeenth day of February, Anno Domini one thousand nine hundred and six,¹ shall remain in office and continue their functions until the expiration of the term for which they were appointed, each board of registration commissioners remaining in charge of the municipal territory for which it was appointed.