Stevens and Ida Clendenin. Among the exhibits, those of twelve species of hepaticæ from California, by Prof. F. E. Lloyd; forty-five photographs of American students and collectors made famous by their work in mosses, by Mrs. Britton and Professor Underwood; and six species of mosses discovered and collected originally by Sullivant and Lesquereux near Columbus, deserve special mention. =Rate of Evolutionary Variation in the Past.=--Mr. Adam Sedgwick, speaking, in his address at the British Association, of variation, selection, and heredity, having raised the question whether the variability of organisms has ever been different from what it is now, answered it in the affirmative, because it would be absurd to suppose that organisms would remain constant in this respect while they have undergone alteration in all their other properties. According to the Darwinian theory of evolution, one of the most important factors in determining the modification of organisms has been natural selection. It acts by preserving certain favorable variations, and allowing others less favorable to be killed off in the struggle for existence. It will thus come about that certain variations will be gradually eliminated, while the variations of the selected organisms will themselves be submitted to selection, and certain of these will in their turn be eliminated. In this way a group of organisms becomes more and more closely adapted to the surroundings. It would thus appear that the result of continued selection is to diminish the variability of a species. Hence, as selection has been going on all the while, variation must have been much greater in past times than it is now. Following out this train of reasoning, we are driven to the conclusion that one of the most important results of the evolutionary change has been the gradual increase and perfection of heredity as a function of organisms and a gradual elimination of variability. This view, if it can be established, is of the utmost importance to our theoretical conception of evolution, because it enables us to bring our requirements as to time within the limits granted by the physicists. MINOR PARAGRAPHS.