tion is not strictly proportional to accelerating force and that kinetic energy is not strictly proportional to the square of the velocity of a moving body.
Up to the present time a very prominent feature of physical science has been the reduction of every kind of phenomenon to mechanics. The notional elements out of which nearly every theory is built up are essentially mechanical in their nature, if one may use the term mechanical in a broad sense to signify all kinds of geometrical, kinematical and dynamical relations. The reason for this preponderating role of mechanics is that, hitherto at least, only those theories are effectively useful which are built up out of sensuous elements, and nearly all our complicated sensations refer to space relations as perceived with the eye and to dynamic and space relations as perceived by the sense of touch and by the so-called muscular sense. It is not likely that the transfer of mechanics to an electromagnetic foundation will greatly affect the preponderating role of concrete mechanics in physical science.
TENDENCIES IN ZOOLOGY.
Zoology also has its fashions. The publication of the 'Origin of Species,' by establishing a new standpoint and new problems, led zoologists to an ever minuter study of comparative morphology, already made fashionable by the work of Cuvier, Johannes Müller and Owen. On the discovery of the chordate affinities of the Tunicates by Kowalewsky, in 1866, an impulse was given to the investigation of comparative embryology, in the hope of further information, which, viewed in the light of the biogenetic law, might add other links to the phylogenetic chain. And later, when the science of cytology came into definite existence, the embryologist, who at first was content to carry his studies back only so far as the gastrula, was incited to delve more deeply, and for a time cell-lineage became the fashion, while, following quickly in the footsteps of this, experimental morphology became a vogue. Not that this last was an entirely new department of investigation, but rather a revival under new conditions and points of view of the methods of study employed by Trembley and Spallanzani whose experimental researches on Hydra and the earthworm respectively have reached the dignity of classics.
The latest fashion, nature-study, as it is called, is likewise a revival of older methods. It is a rejuvenescence of the natural history of the ancients, a return to the methods of Gilbert White, methods which, while they have never failed to attract, have unfortunately been sadly neglected of late by the professional zoologist. The developments of his subject have been towards ever-increasing esoterism, until the stage has now been reached when the laity has lost touch with the professional and fails to appreciate the results which he elaborates in the privacy of his laboratory, surrounded by his complicated engines for cutting sections and his multitudinous reagent bottles. In so far as this new revival of natural history methods may serve to bring about again a rapprochement of the amateur and the professional, it is to be welcomed, and important additions to our knowledge of the habits and instincts of animals and the significance of these may be expected when men, specially trained in the methods of biological investigation and thought, turn their attention to these phenomena.
But the enthusiasm which usually accompanies investigation along a new line must not blind to the danger which lurks beneath. The hope which lies in the departure is that it will tend to place the study of instincts and habits on a scientific basis and yield scientific results founded on careful and accurate observations, that, in a word, it will bring order into the chaos of observa-
