planet D Q, however, discovered by Herr Witt, of the Urania Observatory, of Berlin, on August 13 th last, has aroused from the first special attention through its remarkable behavior. The orbit is a very unusual one. Mars has always been considered our nearest neighbor, although it was known that some of the minor planets were slightly nearer to the sun when at perihelion than Mars is when at aphelion. But the mean distances of the latter were in all cases much greater than that of Mars; while that found for the new planet is only 1.46 as compared with 1.52 for Mars, and, as the eccentricity amounts to 0.23, the perihelion distance is only 1.13, and the least distance from the earth's orbit only 0.15 as compared with 0.27 for Venus in transit, and 0.38 for Mars in perihelion. The planet will thus be far closer to us than any other member of the solar system, and will afford a most excellent means of determining the sun's parallax. Its diameter is thought to be about seventeen miles.
Extra-Organic Factors of Evolution.— Observing that our civilization has made advances or "strides" in recent years out of all proportion to any improvements that have taken place in our organic faculties, Arthur Allin has insisted, in Science, on the importance of extra organic factors in human development. Our sense and motor organs, he says, are essentially instruments and tools, and so is the brain; and most if not all of the three hundred or more mechanical movements known in the arts are found exemplified in the human body. Our sense organs are thus indefinitely multiplied and extended by such extra-organic sense organs as the microscope, telescope, resonator, telephone, telegraph, thermometer, etc. Our motor organs are multiplied by such agencies as steam and electrical machines, etc., in the same manner. "The printing press is an extra-organic memory far more lasting and durable than the plastic but fickle brain. Fire provides man with a second digestive apparatus by means of which hard and stringy roots and other materials for food are rendered digestible and poisonous roots and herbs innocuous. Tools, traps, weapons, etc., are but extensions of bodily contrivances. Clothing, unlike the fur or layer of blubber of the lower animals, becomes a part of the organism at will. One finds himself more or less independent of seasons, climates, and geographical restrictions. By organic heredity or the transmission of the congenital characteristics of the parents to the children, working alone, all progress depends upon the transmission of variations occurring within the organism. "Moreover, these advantageous organic variations die with the individual, and must be born again, so to speak, with each new individual." This requires time, and progress depending on it would be indefinitely protracted. On the other hand, by means of social heredity, each new member of the race has handed to him at birth the accumulated organic advantageous variations of sense and motor organs, and the extra-organic adaptations that have multiplied so indefinitely in the age of civilized man. "The vast importance of accumulation of capital is obvious."
Fossils as Criterions of Geological Ages. —Prof. O. C. Marsh said in a paper on The Comparative Value of Different Kinds of Fossils in determining Geological Age, which was read at the meeting of the British Association, that the value of all fossils as evidence of geological age depends mainly upon their degree of specialization. In invertebrates, for example, a lingula from the Cambrian has reached a definite point of development from some earlier ancestor. One from the Silurian or Devonian, or even a later formation, shows, however, little advance. Even recent forms of the same or an allied genus have no distinctive characters sufficiently important to mark geological horizons. With ammonites the case is entirely different. From the earliest appearance of the family the members were constantly changing. The trilobites show a group of invertebrates ever subject to modification, from the earliest known forms in the Cambrian to the last survivors in the Permian. They are thus especially fitted to aid the geologist, as each has distinctive features and an abiding place of its own in geological time. In the fresh-water forms of mollusca—the Unios, for example—there is little evidence of change from the palæozoic forms to those still living, and we can therefore expect little assistance from them in noticing the succeeding periods during
