The commissioner shall cause a notice of such assessment order, setting forth a brief summary of the contents of such order, to be (a) published in such manner as shall be directed by the court, and (b) enclosed in a sealed envelope, addressed and mailed postage prepaid, to each member or subscriber liable thereunder at his last-known address as it appears on the records of the insurer, at least twenty days before the return day of the order to show cause provided for in section thirty-three of this article.