Mass. Gen. Laws ch. 231 § 61
The provisions of this section and of sections sixty-two through sixty-nine, inclusive, shall be applicable only to civil proceedings which are not governed by the Massachusetts Rules of Civil Procedure or the District-Municipal Courts Rules of Civil Procedure. Any party, after the commencement of an action, may interrogate an adverse party for the discovery of facts and documents admissible in evidence at the trial of the case. No party shall file as of right more than thirty interrogatories, including interrogatories subsidiary or incidental to, or dependent upon, other interrogatories, and however the same may be grouped, combined or arranged; but for adequate cause shown, the court may allow additional interrogatories to be filed. The word "party", in this section, in sections sixty-two to sixty-five, inclusive, and in section sixty-seven, shall be deemed to include parties intervening or otherwise admitted after the beginning of the suit.
Mass. Gen. Laws ch. 231, § 61