days the turnip-juice was perfectly pellucid and free from life. Two days' exposure to ordinary air sufficed to render it muddy. After twelve days the pinch-cock was opened, so as to allow a momentary inrush of the external air, which was immediately checked by the reclosing of the cock. Three days after, the infusion of the test-tube into which the air first entered was muddy, and crowded with life. The contamination did not reach the second test-tube. These experiments completely verify the conclusion that, in Schulze's experiment, water may be substituted for sulphuric acid and caustic potash without any alteration in the result (Proc. Roy. Soc., No. 185).

Action of very Low Temperatures on Bacteria.

While the action of high temperature on Bacteria has been frequently studied, few observations have been made as to their behavior at low temperatures, but it has been found that they stiffen at 0 C., and are not killed at — 18° to −25° C. Herr A. Frisch, by means of solid carbonic acid and ether, exposed some putrefactive fluid Bacteria, and some forms of Coccus and Bacterium in the morbid products of living organisms, to -87.5°, and allowed them in the course of 21 hours to rise to 0°. The result was, that the Bacteria in the fluid withstood this low temperature, and grew rapidly when transferred to a suitable nutritive fluid (Der Naturforscher, No. 5, 1878).

Staining and Preparation of Bacteria.

The difficulties which are involved in the study of Bacteria arise partly from the gaps which appear in the classification of these minutest of all living organisms, and the new forms which are continually cropping up, and partly from the microscopes employed possessing little power of illumination and definition, although furnished with sufficiently high powers; and their investigation is a matter of enormous difficulty on account of their extreme minuteness, their weak refracting power, and their motion. Dr. W. A. Haupt proposes to stain the whole fluid which contains the Bacteria, at the patient's bedside, or the dissecting-table, the microscopical examination to be made at any convenient time. For the purpose of staining, he prefers aniline-violet, fuchsine,

and erythrusine. A trial can be made on Bacterium termo, which is one of the most difficult of preparation. It is easily procured by exposing a piece of raw meat, placed with water in a porcelain cup, to the sun for an hour or two, or letting it stand near a warm oven. When an opal-like scum has formed on the fluid, every drop is seen under the microscope to contain millions of these bodies. This, or any other fluid containing Bacteria (urine, serum, blood, etc.), should be put in a 10-gram glass which has been carefully washed and rinsed in alcohol. The bottle should be a fourth or a fifth part filled, and the same quantity of a solution in water (well filtered) of the staining material added, and then, after being well shaken, corked and labelled. From five or ten minutes to forty-eight hours are required, according to the nature of the object. When examination with the microscope shows the result is satisfactory, a drop is taken from the bottom by means of a pipette and spread out well on a glass slide, and dried in a warm place, protected from dust. A drop of dammar varnish, or Canada balsam, is applied, the covering-glass is pressed down, and the preparation is ready for examination, and may be preserved indefinitely (Zeitschrift für Mikroskopie, vol. i., p. 175).

Examining, Preserving, and Photographing Bacteria.

The principal difficulties which arise in investigating Bacteria are connected with their small size, their movements, their simplicity of form, and their want of color or power of strongly refracting light. Dr. Koch proposes, in order to obviate these difficulties, the following process: A drop of the fluid containing the Bacteria is spread out in as thin a film as possible on the covering-glass and dried. In this condition they may remain for months, if kept from dust, etc., without any change to the dried Bacteria; and, as they dry without shrinking or changing their form, there is no objec tion to this part of the process. The next step is to moisten the film with acetate of potash (one part in two parts of distilled water); the Bacteria resume perfectly their original form, and the fluid answers as a special preservative from further change. They are yet too pale for photographing; for this purpose they must be stained with aniline dye, which they take quickly and completely. Methyl-violet and fuchsine

are especially suitable, or aniline-brown. After the staining, 'they must be dried and mounted in balsam in the usual way. Photographs from specimens thus prepared show the most delicate details, as, for instance, the flagella (Zeitschrift für Mikroskopie, vol. i., p. 119).

Measurement of the Diameter of the Flagella of Bacterium Termo. (A Contribution to the Question of the "Ultimate Limit of Vision" with our Present Lenses.)

The Rev. W. H. Dallinger, already so well known for his observations and studies of Monads, contributes a paper on the above-named subject to the September number of the Journal of the Royal Microscopical Society, full of interest, but of which we can here give only a meagre outline. The paper is illustrated with two fine plates, on one of which are reproduced two of Dr. Koch's photographs, mentioned in the preceding article. Bacterium termo is the smallest of all the group, and although Kock, Warming, and others, had detected the flagella on the larger specimens of other Bacteria, they had never been seen on B. termo, though from analogy they were supposed to be present. The average length of B. termo is about Tʊʊʊ of an inch, and on this minute object, by the most skilful manipulation of Powell & Lealand's most recently improved objectives, and, also, with those of Mr. Tolles, Mr. Dallinger and his coadjutor, Dr. Drysdale, have not only succeeded in demonstrating the flagellum, but have actually measured this fine organic fibre, with the following results: (1.) The mean value of fifty measurements made with the one-twelfth inch objective gives, for the diameter of the flagellum, 0.00000489208. (2.) The mean value of fifty measurements made with the one-sixteenth inch objective gives 0.00000488673. (3.) The mean value of fifty measurements made with the one-twenty-fifth inch objective gives 0.00000488024. The mean value of fifty measurements made with the one-thirty-fifth inch objective gives 0.00000488200. We thus get, for mean value of the whole, expressed in vulgar fractions, 204700 of an inch; so that we may safely state that an atom of a semitransparent structure 2000 of an inch in diameter may become visible under proper conditions of illumination and manipulation.

Life History of a Minute Septic Organism.

The Rev. W. H. Dallinger's paper on this subject, in the Proceedings of the Royal Society, No. 187, 1878, is one of exceeding interest, and is accessible to American readers in the admirable reprint in the American Journal of Microscopy for August, 1878. The story is clearly and conscientiously told, and one feels assured at every step that the author is not only stating facts that hereafter cannot be questioned, but that he is admirably fitted in every way to conduct such delicate investigations. It is impossible in our limited space to do any justice to this paper by an abstract.

Bacteria in Splenic Disease.

M. H. Toussaint claims that in splenic disease death results not from a virus, but from obstruction of the capillaries of essential organs, as the brain and lungs, by the rapid multiplication of Bacteria. Fresh Bacteria blood, received in tubes, and preserved from contact with the air and from putrefaction, loses its contagious properties in six or eight days, or sooner if kept at a temperature of from 38° to 40° C.; but such a method would be adopted to preserve virus (Comptes Rendus, March 18, 1878).

INFUSORIA, DIATOMS, RADIOLARIA, ETC.

Trembley's Experiments in Turning a Hydra Inside Out. Professor Engelmann, of Utrecht, has repeated Trembley's celebrated experiment with negative results. With animals of suitable size, and a hog's bristle of proper size and shape, the experiment was easily performed; they were taken from both slow-running and stagnant waters. He found that the turned body, when it did not soon resume its normal position, always perished within a short time; the cells, and first of all those of the entoderm, swelled very much, gradually loosened themselves from their connection, and were found after a day or two, like a small white cloud, at the bottom of the glass. The experiments in clipping off small pieces of the tentacles, which developed into perfect five-armed Polypi, and with Hydra, which had been slit longitudinally, and readily grew together, proved that the conditions were not

unfavorable for success, and he concludes, therefore, that Trembley sometimes describes things most minutely of which in reality he has seen the least (Zoologischer Anzeiger, vol. i., p. 77).

The Foraminifera and Polycystina of the North Polar Expedition, 1875-76.

The soundings from depths of 10 to 220 fathoms, brought home by the expedition, have been examined by Mr. H. B. Brady. The area is altogether new, and about half a dozen species of Foraminifera may be considered as essential constituents of the Mesozoic fauna of these high latitudes, and these constitute about 95 per cent. of the entire collection. They are, Globigerina bulloides, Cassidulina lævigata, C. crassa, Truncatulina lobatula, Pulvinulina karsteni, Polystomella striatopunctata, and sometimes a few forms of Nonionina. The almost complete absence of the Milioline genera is an unexpected feature, as no approach to a full-sized mature specimen has been met with in the North Polar material. Only a few Radiolaria were observed, and these, according to Professor Haeckel, to whom they were submitted, appear to be identical with those found in the Challenger soundings in the Middle Pacific, at depths of 2400 to 2900 fathoms, from about 8° N. to 8° S. of the equator. By these soundings, our knowledge of the sea-bottom extends to latitude 83° 19′ N., a distance of 6° 49′ more than half the interval between the most northerly point of previous researches and the actual North Pole. The facts which have been elicited appear to indicate that there is no very striking diminution in the number and variety of the Rhizopoda as we approach the North Pole (Annals and Magazine of Natural History, June, 1878).

Radiolaria.

Mr. St. George Mivart's paper on the Radiolaria, printed in No. 74 of the Linnæan Society's Journal, may be commended to all interested in the study of these organisms. condensed treatise on the group.

Multiplication of Rhizopods.

It is a

Professor Leidy has successfully observed the mode of multiplication of the test-covered Rhizopods,which is analogous to