Zygo Corp. of Middlefield, Conn., acquired all outstanding shares of Canada-based NexStar Automation Inc. in exchange for 250,000 shares of Zygo's common stock. The transaction was structured as a statutory plan of arrangement under Canadian law; the shares are therefore not registered in the US. Zygo urged NexStar shareholders to tender their certificates soon to Montreal Trust Company in Vancouver, B.C., Canada, so that they receive the Zygo share certificates to which they are entitled.