sification. Formal parties are those who have no interest in the controversy between tbe immediate litigants, but bave an interest in the subject-matter which may be conveniently settled in tbe suit, and thereby prevent further litigation; they may be made parties or not, at the option of the complainant. Chadbourne v. Coe, 51 Fed. 479, 2 C. C. A. 82,7.—Necessary parties are those parties who have such an interest in the subject-matter of a suit in equity, or whose rights are so involved in the contro-versy, that no complete and effective decree can be made, dispoptyg of the matters in issue and