If the action proceeds to judgment without the interposition of a counterclaim as required by subdivision (a) of this rule, the counterclaim is barred.

It pointed out that under former Equity Rule 30 [Equity Rules, 28 USCA § 723 Appendix (1941)] a defendant in an equity suit was not required to set up a legal counterclaim, but if he did so and went on to trial, he was held to have waived a jury trial.

Equity Rule 30 requires that a counterclaim cannot be set out in a cross-complaint, unless it be the subject of an independent suit in equity against the plaintiff.

Rule 13 (a), 28 USCA Accordingly, federal jurisdiction over the subject matter need not rest upon independent grounds, but may be grounded upon jurisdiction over the subject matter of the main suit

The provision of the act of Congress does not extend to the jurisdiction of the Federal court, but governs the proceedings in equity and, unless the case is one where the objection may be treated as waived by the party entitled to raise it, the prohibition is not to be disregarded.

If the plaintiff were demanding relief upon that basis, the equitable issue would have to be disposed of at the beginning.

—the court, in construing former equity Rule 30, held in effect that in an equitable action a defendant must set forth by counterclaim any cause of action arising out of the subject matter of the complaint; otherwise, a defendant is barred from maintaining an independent action.

The right of the receivers to have affirmative relief in the receivership court is supported by the same, or at least similar and equally strong, reasons as those that constitute the foundation of the rule.

Likewise for Equity Rule 30, which was "intended to simplify equity pleading and practice by limiting the pleadings to a statement of ultimate facts without evidence and by uniting in one action as many issues as could conveniently be disposed of."

In such a case, the defense of fraud is completely available in the action at law, and a bill in equity would not lie to stay proceedings in that action in order to have the defense heard and determined in equity.