If the assets, after payment of debts, necessary expenses and specific legacies, are not sufficient to pay all the general legacies in full, the latter shall abate or be diminished in equal proportions, and, in the absence of any direction to the contrary in the will, the executor has no right to pay one legatee in preference to another, or to retain any money on account of a legacy to himself or to any person for whom he is a trustee.