Mass. Gen. Laws ch. 203A § 1
Any individual, corporation or association qualified to act as fiduciary in this state may establish common trust funds for the purpose of furnishing investments to itself as fiduciary or to itself and others, as co-fiduciaries; and may, as such fiduciary or co-fiduciary, invest funds which it lawfully holds for investment in interests in such common trust funds, if such investment is not prohibited by the instrument, judgment, decree or order creating such fiduciary relationship. Each such common trust fund shall be administered in accordance with a written declaration of trust which shall have been filed in the registry of probate in the county in which such individual, corporation or association resides or has his or its principal place of business, and such written declaration may provide that premiums paid on the purchase of interest bearing securities need not be amortized.
Mass. Gen. Laws ch. 203A, § 1