ยง 303. Designation of attorney as agent for service. The commencement of an action in the state by a person not subject to personal jurisdiction is a designation by him of his attorney appearing in the action or of the clerk of the court if no attorney appears, as agent, during the pendency of the action, for service of a summons pursuant to section 308,in any separate action in which such a person is a defendant and another party to the action is a plaintiff if such separate action would have been permitted as a counterclaim had the action been brought in the supreme court.