25.-(1) Every answer which contains matter other than a simple denial of the facts stated in the petition shall be accompanied by an affidavit made by the respondent verifying such other additional matter so far as he or she has personal knowledge thereof and deposing to his or her belief in the truth of the rest of such other additional matter, and where the respondent is husband or wife of the petitioner shall further state, except where the claim in the suit is for restitution of conjugal rights, that there is not any collusion or connivance between the parties. Such affidavit shall be filed with the answer.
(2) Where the answer of a husband alleges adultery and prays relief, the alleged adulterer must be served personally with a sealed copy thereof bearing a notice to appear in like manner as a petition. Where in such a case no relief is claimed the alleged adulterer shall not be made a co-respondent but a sealed copy of the answer shall be delivered to him indorsed with notice as under rule 20 that he is entitled within eight days after delivery thereof to apply for leave to intervene in the cause and that upon such application he may be allowed to intervene subject to such directions as shall then be given.