IN Dr. Wright's interesting review of “Les Grottes de Grimaldi,” by M. L. de Villeneuve (NATURE, October 10, p. 590), I find the following:—“M. Riviere attributed them [the deposits] to the Quaternary period, M. Mortillet, on the other hand, regarded them as Neolithic.” Now it is impossible to conceive any defensible use of the word “Quaternary” that does not include the Neolithic. Many authors have condemned the expression on the ground that the Pleistocene and Recent are nothing more than the latest and very subordinate portions of the Tertiary period. For my own part I believe that the great influence which man has already exerted on the character and distribution of the forms of life upon the earth, as well as on the purely physical conditions of its surface and the still greater changes that his activity must occasion even in the near future, are ample justification for marking his effective appearance on the scene by the commencement of a new period in the earth's history, a period the threshold of which we have scarcely passed. If, however, the Quaternary “period” is to be considered to close at the end of the Pleistocene, it becomes so insignificant in comparison with the long ages of its predecessors that it would be better to dispense with it altogether.