This was an action of tort, in the nature of trespass quare clausum fregit. The plaintiff, to prove his possession, offered evidence that he was in under Wagner, one of the defendants, who had been defaulted. His possession we infer was that of tenant at will, and as such was sufficient to support his action. The defendants offered in defence a written lease of the premises from said Wagner to one Gergler, and further offered evidence that they did the acts complained of as the agents and by the command of Gergler. And the question is, whether this evidence was admissible under the answer. The case is governed by the rules of pleading established by the practice act, the purpose of which was to secure more effectually full notice to the plaintiff of the specific grounds upon which the defence is to be placed, The answer here is a general denial of the plaintiff’s allegations. If the evidence offered tended to disprove a material allegation in the writ, it was competent; but if to sustain an independent substantive matter of defence not involved in the pleadings of the parties, then it was rightly rejected.

fhe execution of the lease did not terminate the plaintiff’s possession; it did no more than change that possession from that of tenant at will to that of tenant by sufferance. But as tenant of the latter description the plaintiff had sufficient possession to maintain trespass against strangers. And proof of the execution of the lease to Gergler therefore was wholly immaterial, without further evidence offered by them that they entered and did the acts as agents of the lessee. It was this evidence of the relation which the defendants sustained to Gergler, disclosing a fact not embraced in the allegations necessary to support the plaintiff’s case, but necessary in order to iefeat the plaintiff’s possession as against them, and without *420which the execution of the lease amounted to nothing, which we think required an allegation in the defendants’ answer to render it admissible. The plaintiff would have no means of knowing, even if he had been informed of the lease, that these defendants acted as agents of the lessee. It was a substantive matter in defence, and should have been pleaded. It was in the nature of a justification under the license and authority of a third person having, as it was claimed, title and possession of the premises. Mulry v. Mohawk Valley Ins. Co. 5 Gray, 541. Knapp v. Slocomb, 9 Gray, 73. Snow v. Chatfield, 11 Gray, 12. 1 Chit. Pl. (6th Amer. ed.) 161. Exceptions overruled*