This is a suit for patent infringement. Issue has been joined herein by the service of an answer. The plaintiff now moves to file a reply in which he seeks to set up new matter for the purpose of establishing an estoppel against the defendant from asserting defenses to the cause of action alleged. Because of the confusion which would result from such a course, the court in the exercise of its discretion will permit the plaintiff to serve an amended complaint in which he may set up his cause of action together with any matter which is claimed by him to constitute an estoppel against the defendant from asserting particular defenses thereto. The defendant may then answer or move with respect to the amended complaint in any manner which it may be advised.