The spots commenced to show themselves, but the tissue withered on all the leaves: the parasites only developed in a very incomplete manner, and did not appear the following year. The fungus is therefore entirely localized on the foliar and deciduous organs; it is fully developed only on the young organs.

It appears then that it would be sufficient to produce the disappearance of the Rhytisma to destroy all the spotted leaves which fall in the autumn, but this presupposes that the small corpuscles (spermatia of Tulasne), produced in enormous numbers on the living leaves (Xyloma), are not able also to produce the parasite.

The red spots of the plum tree, produced by the Polystigma rubrum, an ascomycetous fungus of quite another group, and much more dangerous, have probably a very analogous history.*

The Reproduction of Hydra (Note by M. Korotneff, communicated by M. de Lacaze Duthiers to the French Academy)." In spite of its abundance, the fresh-water Hydra presents a great number of peculiarities insufficiently studied, and particularly the reproduction of the sexual elements, and the embryonic development of the individual itself.

These phenomena have been described in a fairly detailed manner by Kleinenberg, in his 'Monograph of Hydra.' According to his researches, the cells are found below the ectodermal elements (interstitielles Gewebe), and form an agglomeration which serves to reproduce the ova as well as the spermatozoids. The development of the ovum is accomplished as follows: one of the cells of the agglomeration increases remarkably, and swallows up the surrounding cells -in other words, it feeds itself upon them. The nucleus is changed into a germinal vesicle, and at last, the cell itself represents the ovum of the Hydra, which is thus, according to its origin, a monocellular and ectodermic formation.

The granulations of a definitively formed ovum serve to produce the larger elements, which Kleinenberg describes under the name of pseudo-cells (Pseudocellen, Kl.).

After a detailed description of the segmentation, the German savant passes to the formation of the blastoderm, as an immediately succeeding phenomenon to segmentation. The blastoderm consists of a layer of cells, forming by itself the entire envelope of the ovum. Kleinenberg considers the blastoderm to be an embryonic epithelium, not taking part in the ulterior formation of the Hydra, and thrown off as an envelope at a certain period of the development; for this reason the adult Hydra is an animal destitute of epithelium.

My own researches, made upon Hydra fusca, completely contradict those of Kleinenberg. Nevertheless, conformably with his researches, I have seen an agglomeration of cells, of ectodermic elements, which I consider simply embryonic cells, which serve to reproduce different ectodermic elements. One of these cells grows, and its nucleus changes into a germinal vesicle. At the same time, the peripheral elements of the agglomeration separate, forming a row

* M. Max Cornu, in 'Comptes Rendus,' vol. lxxxvii. p. 178.

of cells by means of small, highly refractive granules, while the central cells are joined to each other and to the enlarged cell; in this manner, a common plasmodium is formed, strewn with a considerable number of nuclei. The germinal vesicle begins to degenerate, and disappears entirely (this last phenomenon agrees with the observations of Kleinenberg); but the nuclei of the central cells undergo a transformation of another sort; they increase somewhat in size and degenerate into fatty bodies; at the same time certain of them divide (their nucleoli also take part in this division). The degeneration of à nucleus begins by a considerable increase of its nucleolus, which becomes highly refractive and ends by being blended with the contents of the nucleus. It is these degenerated nuclei, probably serving for the nutrition of the embryo, which Kleinenberg takes for pseudocells. The peripheral elements of the agglomeration, strewn with granules of a chitinous origin, serve to form the shell or the envelope of the ovum.

In comparing my observations with those of Kleinenberg, I conclude that the German savant has taken the peripheral cells of the agglomeration for a blastoderm, and the mass of central cells for an effect of segmentation of the ovum. According to my observations, Hydra evidently cannot be regarded as an animal destitute of epithelium: my former researches have established the fact that this epithelium is muscular.' "*

The Staining and Preparation of Bacteria. In the Zeitschrift für Mikroskopie' Dr. W. A. Haupt explains his views as to how the staining and preparation of bacteria may be facilitated.

After referring to the development in recent times of the doctrine of a contagium vivum, and the fact that scarcely a medical periodical can be taken up but we meet with articles on the etiology of infectious diseases with reference to bacteria, Dr. Haupt complains that from the inexperience of the authors or their defective microscopical observations these articles tend rather to obscure than elucidate the subject. He instances a paper by Dr. Tschamer which appeared in the same journal, in which hooping cough is attributed to the presence of the Ustilago Maydis, and its oidium from Capnodium Citri. Dr. Haupt maintains that the Ustilagine have not the oidium form, and that this parasite being found exclusively on maize, it is strange that the disease should flourish where there is no maize, and be rare where it is cultivated in abundance. It is far more probable, he thinks, that it is produced by a kind of Micrococcus similar to the Micrococcus diphthericus. The presence of spores and fungi in cases where there is no hooping cough is a fact known to everyone who has had much to do with the microscopical examination of the contents of the oral cavity, and, as a case in point, Dr. Haupt relates how, together with Micrococcus diphthericus, &c., he found spores of Tilletia caries in the pus taken from a boy who was suffering from diphtheria. These, he concluded, had nothing to do with the disease, but were attributable to the atmosphere in which the boy lived being impreg* Comptes Rendus,' vol. lxxxvii. p. 412.

nated with flour dust, and, on inquiry, he learned that the boy's father was a pastry-cook.

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, although furnished with high powers, possessing little power of illumination and definition, whilst the investigation of bacteria is a matter of enormous difficulty on account of their extreme minuteness, their weak refracting power, and their motion. By Dr. Koch's process, however, photographs of bacteria will be obtained showing not only their contours, but any flagella or other details, and thus correcting the false ideas founded on erroneous drawings, and paving the way to fresh discoveries. It is confidently predicted that in many kinds of pathogeny where a morphological distinction cannot be discerned, but which are the cause of complaints of a most diverse nature, there will be quite characteristic differences discovered.

Dr. Haupt speaks in the highest terms of Dr. Koch's method, but says that for the practical physician it is too tedious and troublesome. His modification if it consists in staining the whole fluid which contains the bacteria, instead of each preparation by itself. This involves but little expenditure of time and trouble, and can be done at the patient's bedside or at the dissecting table if he be provided with a bottle in which to put the substance to be stained, and another containing the staining fluid. The microscopical examination may be subsequently made at any convenient time, and the bacteria are as clearly seen as when Koch's method is used.

The fluids which Dr. Haupt employed were carmine, eosin, rose de Magdala, hæmatoxylin, parme, anilin-violet, fuchsin, and erythrusin, and, except with the first two, he obtained good results. Hæmatoxylin stained Micrococcus very quickly. He recommends as best

anilin-violet, fuchsin, and especially erythrusin.

Bacterium termo, though difficult of preparation, should be first experimented with, as what answers with it will succeed with all bacteria. Bacterium termo 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, &c.), should be put in a 10-gramme glass which has been carefully washed and rinsed with 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, it is to be corked and labelled. It is well to write on the label its contents, date, and hour. With some objects the staining is effected in five, ten, or fifteen minutes, others require twenty-four to forty-eight hours. After being assured by examination with the microscope that the result is satisfactory, a drop is then taken by means of a pipette from the bottom, and spread out well on a glass

slide and dried in a warm place (well protected from dust), which takes about ten or fifteen minutes. A drop of dammar varnish or Canada balsam is added to it, and the covering glass pressed down as much as possible. The preparation is then ready.

As compared with preparations made by Dr. Koch's method, the ground appears a little more coloured. Since, however, the bacteria are considerably darker, and as high powers must necessarily be used, in which case the colour of the ground causes no inconvenience, the method is strongly recommended to those who have a limited time to devote to microscopical manipulating.*

A Mineralogical Microscope.-M. Renard describes, in the 'Bulletin of the Belgian Microscopical Society,' a new microscope intended for the examination of microscopic crystals by polarized light. One of the leading pecularities of its construction consists in the contrivance (apparently adopted for economical reasons) by which the objective is centered upon the object on a rotating stage. The tube of the microscope carrying the object-glass is enclosed in a fixed outer tube, which is contracted at the upper part so as not to allow of any "pivoting" of the inner tube at that end. Below the contracted part there is a space between the outer and inner tubes, the former being lined with parchment, which is pressed against the latter by springs. Through the lower end of the outer tube work two screws at right angles to each other, which press against the inner tube and move it in two rectangular directions (or any intermediate one), so that it can be readily brought into the correct position.

Alcoholic Fermentation.-An interesting series of experiments was lately instituted by Herr Muntz, in order to determine whether the living cells of the more highly organized plants, when entirely cut off from oxygen, are equally able with the cells of fungi to produce alcoholic fermentation. For this purpose he experimented with a variety of plants, beet, maize, cabbage, chicory, portulacca, nettles, &c. From each kind three equally healthy plants were selected. One was left in the open air, and the other two were placed, with the accompanying soil, under capacious bell-glasses containing an atmosphere of nitrogen, the oxygen being removed by pyrogallic acid. After a lapse of from twelve to forty-eight hours, they were removed from the glasses. One was placed in the open air in order to be certain that the power of development was retained after the imprisonment, and the other was cut off above the ground, distilled with water, and tested for alcohol. In all cases the plants which had been in an atmosphere free from oxygen showed appreciable quantities of alcohol, amounting often to a thousandth of the entire weight of the plant, while no traces could be detected in the plant which had remained in the air during the same time.†

Alcoholic Fermentation.-M. Berthelot recently published, in the 'Revue Scientifique,' what purported to be a copy of some notes (written in October 1877), which were found after his death amongst the papers *Zeitschrift für Mikroskopie,' vol. i. p. 175. + Nature,' vol. xviii. p. 504.

of the late Claude Bernard. These notes, to quote M. Pasteur's words, are an absolute condemnation, without any restriction, of my views on the subject of fermentation in general, and alcoholic fermentation in particular." M. Pasteur took the matter up with some warmth, and the Comptes Rendus' of 22nd and 29th July contain two communications which he made to the Academy, together with the rejoinders of M. Berthelot. M. Pasteur considers he has established that the notes of M. Bernard refer to experiments only just commenced, and which Bernard intended to repeat and check. This view M. Berthelot does not appear to controvert. M. Pasteur concludes by saying that "he is resolved to repeat the experiments of Claude Bernard, and that on a scale and with a fulness of results worthy of the subject and the respect due to the deceased. M. Berthelot applauds this resolution, and anticipates beneficial results to science, "which lives by observations and contradictions. Since the discoveries of M. Pasteur have fixed our ideas of the origin and multiplication of the organized beings which propagate fermentations, a new problem has been presented. The point is to know whether the chemical change produced in every fermentation is not resolved into a fundamental reaction, excited by a definite special principle of the order of soluble ferments, which in general consumes itself proportionately to its production—that is, transforms itself chemically during the very accomplishment of the result which it causes. To recognize such a ferment, we must know how to isolate it; that is, to ascertain the special conditions under which the soluble ferment is secreted in a greater proportion than it is consumed.

The definite relation between the soluble ferment and the microscopic being which forms it has been pointed out, I believe, for the first time with precision, in my researches on the inverting ferment contained in the cells of beer-yeast. It has been found since in the ammoniacal fermentation of urea and elsewhere. It may be well to examine now whether it can be extended to alcoholic fermentation itself —that is, whether some particular condition can be discovered such as those which Claude Bernard seems to have perceived-a condition in which the matter which provokes the alcoholic decomposition of the sugar is formed in an excessive proportion, and consequently capable of being isolated. Alcoholic fermentation would then, as is the case already with most of the others, be brought back to the purely chemical actions."

The Structure of the Brain in different Orders of Insects.-The Supplementary vol. xxx. of Siebold and Kölliker's Zeitschrift für Wissenschaftliche Zoologie,' contains an elaborate article by J. H. L. Flögel, illustrated by a number of microphotographs. This and Dietl's excellent paper, published in 1876, are the only treatises on the minute structure of the brain of insects, Owskianikof having studied that of the spiny lobster Palinurus several years ago, while Dietl studied the brain of Astacus. Flögel establishes three points as the results of his researches.

First, the constant presence of the remarkable central body in the mature insects of all orders, while it is almost absent in the larvæ of