Participation by affiliates.) Any bank or trust company may include for the purpose of collective investment in any common trust fund or funds established, maintained and administered by it, funds held by an affiliate in its capacity as fiduciary or co-fiduciary, provided that the funds so held would be eligible for investment in the common trust fund or funds, had such common trust fund or funds been established, maintained and administered by the affiliate. Such participation by an affiliate may be pursuant to agreement providing for payment of reasonable compensation by the affiliate to the bank or trust company maintaining the fund or funds.