It is a real novelty to have such a lecture as will be delivered to-night in Boylston, among the evening entertainments of the week. The custom, into which so many of our college societies have fallen, of inviting one or more lecturers to Cambridge to address them each year, is extremely suggestive of the interest that is taken in special branches, and pays no slight tribute to the much talked of elective system. The cordiality with which all the societies have extended to the members of the college at large the privilege of attendance deserves no less commendation than this enterprise in giving, often at considerable expense, the different lectures. We believe that this is the first time that the Natural History Society has undertaken anything in the line of public lectures. But we do not doubt that the success of to-night's lecture will justify a second attempt at some future time. The subject and the lecturer who presents it cannot fail to draw a good audience. Mr. Trelease is an interesting and eloquent speaker. Moreover, the fact that the lecture is to be illustrated will add to its value and interest.