ent chicks. No significant effect followed the feeding with slugs or sow-bugs, but the chicks fed with earth-worms developed symptoms of gapes. Experiments were made in artificial culture, and are described in the author's paper. For prevention of gapes, Dr. Walker recommends keeping the chickens away from the ground by putting them on floors, and destroying the earth-worm and its parasite by some preparation fatal to both, such as common salt; asafœtida and garlic, which have been relied upon to cure or prevent gapes, had no effect upon the Syngamus.
Dr. Bickerton's Experiments in Color-Blindness.—T. H. Bickerton, of the Royal Ophthalmic Hospital, Moorfields, has recorded the results of his personal examinations of 5,087 subjects, during five years, for color-blindness. Holmgren's tests were used. Of 3,087 men and boys tested, 179 failed at the first test (a very pale, pure green), either by omitting green, or by putting in some other color. Of these, 74 passed successfully the remaining tests, and were considered to have but a very slight chromatic defect, which might be disregarded. Rejecting these, there were 105 cases of color-blindness, or 3·40 per cent of the whole number. Of 1,841 women and girls examined, 3 only, or 0·162 per cent, were to a greater or less extent affected, and of these one so slightly affected that it was cast out, leaving 2 pronounced cases, or 0·108 per cent. Sixty-four male lunatics afforded 1 complete and 1 incomplete case, while 95 female lunatics were all correct. The social status of these and other persons examined varied from the lowest to the highest, and the ages ranged from five years upward. A large majority of them were under twenty-one. Besides those included under the head of very slightly color-blind, there were others whose color-perception was feeble. Among the lower social grades, as represented by the children in orphanages and reformatories, a considerable number made mistakes in the examinations, and these errors were made not only by those of dullish intellects, but also by those who, according to their mistresses, were sharp girls. Cases of this kind were retested after some months' tuition in colors, and in most instances, where ignorance was suspected, the second trial proved the correctness of that conclusion; but there were others who, although they fulfilled the test, did it with the utmost difficulty. Of the 105 cases of color-blindness, Dr. Bickerton further remarks: "Not one so affected was aware of the defect, and a number of them do not believe it to this day. It may seem curious that people who can not distinguish as different colors red, green, and brown, and in some few cases blue and yellow also, do not themselves discover their peculiarity in their vision for colors. Yet, strange as it may be, so it is, and you will find it exceptional for a color-blind to realize in the first instance the defect himself."
Effect of Climatic Changes on Species.—Any theory of the distribution of species, to be acceptable, must take account of the great gaps which appear in the extension of many kinds. Mr. Edward Forbes and many other modern botanists believe that the question is one of changes of climate; or that the climatic variations of the past are reflected in the fauna and flora of the present. Their views are partially confirmed by the observations which Professor A. Blytt, of the University of Christiania, has made of the climatological relations and the distribution of plants in Norway. Nearly all the climatological lines there run more or less in the shape of the coast, so that the climates are ranged in bands, the changes being observed as one goes from the interior toward the sea, or vice versa. In keeping with the same are the variations of the flora. The plants may be divided into groups, wherein the species belonging to the same group have a somewhat similar extension, while each of the groups is confined to special climatological conditions, and is found only in those parts where the conditions corresponding with its nature prevail. The flora is generally monotonous; but there are certain places dependent partly, perhaps, on the character of the soil, but as much upon exposure to the sun and protection from the changeableness of the coast climate, where a rich vegetation may be found. The flora is destitute of peculiarly characteristic species, because it has come to the country by immigration after the Glacial period, from other countries which were
