A quitclaim deed with or without convenants from the mortgagee should be considered an effective assignment only if executed prior to the most recent validation statute and if it contains specific reference to the mortgage, indicating an intention to assign the same. As to instruments not thus validated, proof must be produced that at the time of the conveyance the mortgagee was in possession of the premises, or that the conveyance was accompanied by an assignment or other transfer of the mortgage debt.