The petition shall be signed by qualified electors of the municipal corporation, equal in number to 10 per centum of the qualified electors, computed upon the total number of votes cast in the municipal corporation for all candidates for Governor at the last preceding general election prior to the filing of the petition at which a governor was elected. The petition may consist of separate papers, but if any paper consists of more than one sheet it shall be securely fastened together at the top. The signatures need not all be appended to one sheet of paper. Each paper shall have attached, at the bottom of the last sheet, the affidavit of a qualified elector of the municipal corporation, stating that all of the signatures on each sheet were made in his presence, and that to the best of his knowledge and belief each signature is a genuine signature of the person whose name purports to be subscribed.