When it appears by the answers of a trustee that any goods, effects or credits in his hands are claimed by a 3rd person by virtue of an assignment from the principal debtor or in some other way, the court may permit such claimant to appear, if he sees cause. If he does not appear voluntarily, notice may be issued and served on him as the court directs. If he appears, he may be admitted as a party to the action so far as respects his title to the goods, effects or credits in question, and he may allege and prove any facts not stated or denied in the disclosure of the trustee. If he does not appear in person or by attorney, the assignment shall have no effect to defeat plaintiff's attachment.