SEPTEM B ER I 8, I 902] NATURE 491 the figures of the genera l appearance a re good, but the sketches of details, as, for instance, the utricles, are too small to help much in determination of species. They would be more satisfactory if they were drawn natural size or larger. The book is written in English. An Arithmetic for Schools. By J. P. Kirkman, M.A., and A. E. Field, M.A. Pp. lxvi + 492. (London : Edward Arnold, n.d.) Price 3s. 6d.