Page:Popular Science Monthly Volume 6.djvu/652
THE POPULAR SCIENCE MONTHLY.
ten iron. The latter fact shows simply that solid iron, when at a high temperature, approaching its melting-point, is less dense and lighter than molten iron, which fact again implies that molten iron must undergo a rapid expansion in the moment of its solidification. The extent of this expansion is, however, less than that of the subsequent contraction in cooling, so that the cold iron is again denser than the molten iron."
Growth of Plants within the Egg.—Prof. Panceri's observations and experiments on the production, of cryptogamic vegetation in eggs are interesting, from their bearing on the question of spontaneous generation. At Cairo, an ostrich-egg was given him which was still fresh, the airspace having not even been formed. He soon, however, noticed the appearance of dark blotches within the shell, and, having broken it to ascertain the cause, he found that they were produced by the growth of minute fungi. The partisans of spontaneous generation look on such cases as that as an argument in their favor, supposing the shell of an egg to be quite impermeable to germs derived from without. Panceri, on the contrary, has found that the unbroken shell of an egg is permeable to liquids, and that these may introduce germs into the interior. He has, in fact, actually inoculated uncontaminated eggs with a fungus obtained from the interior of one in which it had made its appearance in a way seemingly so mysterious, and which he had cultivated in egg albumen.
Huxley on the Cell-Theory in Physiology.—In seconding a motion of thanks to Prof. Redfern, President of the Biological Section of the British Association, Mr. Huxley said that the promulgation of the cell-theory had as great an effect upon the physiological world as the French Revolution had on the world of politics. Referring to the doctrine promulgated by Schwann and Schleiden, he said that underneath that doctrine there lay the idea which had been established by every further observation, and which remained unassailable, viz., that the living body was not a simple continuous whole, and its action was not the action of a unity, but that it was made up of a multitude of parts, which lived a quasi-independent life; and that the body of a man was made up of an enormous multitude of small living particles, each of which, though subordinated and kept together by means referred to by Prof. Redfern, led a quasi-independent life, as did the cells of the organic elements of a plant. It was, in fact, the application to animal-structure of the idea which had been previously applied to plant-structure.
The Deep-Sea Bottom.—In the "Preliminary Notes" of the Challenger Expedition, presented to the Royal Society of London by Prof. Wyville Thomson, are to be found some observations on the Globigerina and on the sedimentary formations at the bottom of the sea, which mark a substantial advance in the science of these subjects. The globigerina is a minute foraminifer, the shells of which constitute the great bulk of the chalk formation. An ocean sediment known as the "globigerina-ooze" also consists principally of these shells, and hence it is to be regarded as a true chalk formation. Hitherto Prof. Wyville Thomson and Dr. Carpenter have supposed that the globigerina is an inhabitant of the sea-depths, while other English, as well as American and German, naturalists have insisted that it is a surface animal. In these "Preliminary Notes," Prof. Thomson very frankly admits the erroneousness of his own view. In fact, the living globigerina is, he says, very different in appearance from the dead shells we find at the bottom of the sea. In the living animal the shell is clear and transparent, and each of the pores which penetrate it is surrounded by a raised crest, the crest round adjacent pores coalescing with a roughly-hexagonal net-work, so that the pores appear to be at the bottom of an hexagonal pit. At each angle of this hexagon the crest gives off a delicate, flexible, calcareous spine, sometimes four or five times the diameter of the shell in length. These spines radiate symmetrically from the direction of the centre of each chamber of the shell, and the sheaves of long, transparent needles crossing each other in different directions have a very beautiful effect.
The nature of the deposit at the bottom