It may perhaps be interesting to learn that Jews sometimes imitated their bitter enemies in this work of mutilation. Thus in the later editions of the _Book of Genealogies_ by Abraham Zacuto,(219) a passage was left out reproducing the evidence given by the widow of Moses de Leon to the effect that the cabbalistic work, the Zohar, was a forgery manufactured by her poor dear husband. Another omission of this kind is to be found in the Code of R. Joseph Caro, mentioned above. Here the earliest editions declare, in the heading of section 605, “a certain religious usage” to be “a custom of folly.” In the republications, the last three words were left out. From such nonsensical omissions and changes only the earliest editions, which are abundant in the Museum, were exempt. A remarkable feature about the books of this Hebrew collection also is that many of them are provided in the margin with manuscript notes by their former possessors. These often happen to bear very great names in literature. I shall only mention here R. Jacob Emden, Almanzi, Michael, Gerundi, and Heidenheim. Of the works written by R. Jacob Emden, the Museum possesses an almost complete author’s copy with abundant corrections, notes, and emendations by the author himself. His works are still very popular among Polish and Russian Jews, especially his Prayer‐ Book, and his Responses. It would be advisable for publishers in these countries to avail themselves of this copy on the occasion of a new edition. Of Christian scholars I should name here Isaac Casaubon. A rather amusing mistake occurs in Ben‐Jacob’s _Treasure of Books_ in connection with this name. Among the many valuable copies of Kimchi’s grammatical work _Perfection_,(220) possessed by the Museum, there is included one which belonged to Casaubon, and is full of notes by him. The author of the _Treasure_ speaks of a _Perfection_ with notes by Rabbi Yitzchak Kasuban. I was at first at a loss to guess who that Rabbi Casaubon might be. When examining Zedner I found it was no other than the famous Christian scholar, Isaac Casaubon. It is not known that Casaubon’s ambition lay in this direction. But when Philo was regarded as a Father of the Church, Ben Gabirol quoted for many centuries as a Mohammedan philosopher, why should not Casaubon obtain for once the dignity of a Rabbi?