20. Where a husband is charged with adultery with a named person a sealed copy of the pleading containing such charge shall be delivered to the person with whom adultery is alleged to have been committed, but instead of being indorsed with notice to appear it shall be indorsed with notice that such person is entitled within eight days after delivery thereof to apply for leave to intervene in the cause. Such delivery and notice may only be dispensed with by order of a Judge for cause shown. A form of notice is contained in Appendix C.