11. Upon any such petition presented by a husband, the petitioner shall make the alleged adulterer a co-respondent to the said petition, unless he is excused from so doing on one of the following grounds, to be allowed by the Court:- (1) that the respondent is leading the life of a prostitute, and that the petitioner knows of no person with whom the adultery has been committed; (2) that the name of the alleged adulterer is unknown to the petitioner although he has made due efforts to discover it; (3) that the alleged adulterer is dead.