Massachusetts General Laws Part III. Courts, Judicial Officers and Proceedings in Civil Cases (Ch. 211-262) Ch. 246, § 8

The plaintiff may at any time insert the names of other trustees in the summons, and cause the summons to be served upon them; and after service upon a trustee, a plaintiff may cause the summons to be again served upon the same trustee in the same manner and with the same effect as if he had not been previously served. A summons served upon a trustee after service upon the defendant shall be again served upon the defendant.