added, in two hours 90 per cent. alcohol, and, later on, absolute alcohol. In two days all the specimens will be found to be quite hardened. When stained (he recommends picrocarmine in pretty weak solution, and soaking for several days), all the Planaria thus treated preserve their histological structure perfectly well. There is inconvenience in imbedding in paraffin, as in consequence of the great wrinkling the parenchyma of the body is torn asunder. However, by gradually applying turpentine in a strong solution of paraffin this wrinkling can be avoided.

By this method the most delicate Planaria, as e. g. Leptoplana, Proceros aurantiacus, cristatus, Thysanozoon, &c., can be prepared so as to partly retain the colours they possessed when living.*

"Commercial Microscopy."-At the "Écoles Supérieures de Commerce et d'Industrie of Rouen has been established a course of instruction on the application of the microscope to commercial purposes. Dr. Pennetier, the Director of the Museum of Natural History at Rouen, who has taken charge of the course from its commencement, has addressed a note to the Journal de Micrographie,' detailing the objects he has had in view and the specially satisfactory results hitherto obtained, and urging upon the other commercial schools of the country that they should follow the initiative of Rouen and establish a similar course. Many of the pupils of the Rouen school have owed their admission to the large industrial establishments to the expertness in microscopical manipulation which they acquired under Dr. Pennetier's instruction. It is intended to publish the Doctor's lectures, which include not only the adulterations of food, but the recognition of the nature and proportion of the different kinds of fibres in particular materials, the origin and quality of the hairs employed in hat making and the fur trade, the raw material of which any given paper is composed, the discrimination of true ivory from the substances used for it, and a variety of similar matters. This subject also formed the basis of the recent address of the President of the Quekett Microscopical Club.

Physiology of the Contractile Vacuoles of the Infusoria.-The following observations made by Professor Th. W. Engelmann are adduced by him as demonstrating what hitherto has only been a matter of conjecture, that the contractile reservoirs of the Infusoria empty their contents externally on contracting. A new Infusorium which he was examining (which may be called Chilodon propellens), was the size of a medium specimen of Chilodon cucullulus, and accords with this species also in the limitation of the stripes and cilia on the ventral surface, as also in the presence of a discharging cytostom, in the anterior third of the body, and a simple nucleus in conformity with it. The shape is, however, slender, and towards the posterior end, in which the large contractile bladder is placed, the body is more roundly turned. Thus an approach is made of the hypotrichous to the holotrichous type, which is interesting from a systematic point of view.

The animal swam about with a generally constant but very

*Zoologischer Anzeiger,' vol. i. p. 14.

slight motion, for the most part in slight curves. Whenever the contractile reservoir became contracted, which occurred pretty regularly at intervals of about half a minute, and took place very suddenly, there succeeded a jerking kind of acceleration of the forward movement. If the animal happened to be previously stationary, it made a jerking forward movement at the instant of the systole of about a quarter its length. A simultaneous acceleration of the very sluggish ciliar motion could not be discerned at all. The phenomenon can only be explained, therefore, by the rebound caused by the fluid ejected from the contractile bladder at the systole.

With this harmonizes the fact that the hindermost section of the body shrunk together at the systole into a thin, empty, longitudinally folded sac, without there being any appearance of even the slightest increase of volume of the front part of the body. It is certain, therefore, in the case before us, that a very large portion, perhaps the whole quantity, of the fluid contents of the contractile bladder was emptied outwards during the systole.

As the re-expansion of the bladder, as is generally the case, took place very slowly, it could not be decided whether any fluid could be directly sucked in from without. He considers this, however, to be highly improbable, amongst other reasons, because he never succeeded even with other species in seeing the contractile vacuoles fill themselves with coloured fluid from that which surrounded them.*

White of Egg as an Imbedding Substance. The best substance for imbedding small objects with a view to the preparation of sections is one that can be hardened to any required degree, is easily cut, is transparent, and allows of the section being placed in balsam or dammar immediately after it is prepared.

These requisites are found in the ordinary white of egg of the fowl.

The object to be imbedded (which is best stained beforehand) must have lain for one or more hours, according to its size and penetrability, in white of egg, so as to become thoroughly penetrated by it. There must be no alcohol left in the object, as it gives rise to blisters in the course of the subsequent process, and thereby produces holes in the imbedding substance.

The object thus soaked is now placed in an oblong box of stiff close-made paper folded or pasted together filled with the albumen. The position of the object may be fixed if necessary by a needle passing through the upper part of the box, which can be easily withdrawn after the hardening.

The box thus filled must be exposed to hot steam or, still better, to hot air. After about twenty minutes the albumen becomes hard enough, and the box should then be put into strong spirit, which in the course of a few days must be changed once or twice, to be finally replaced by absolute alcohol. Several days after this treatment the objects are ready for cutting. The paper walls of the box may be removed with a knife, and a section of the hardened albumen several

* Zoologischer Anzeiger,' vol. i. p. 121.

millimetres thick taken off, which can be afterwards used for pinning small objects on before placing them in the box.

The dried (dehydrated) pieces can now be cut by the microtome into sections mm. thick, and the section placed at once on the glass slide, where it may be treated as usual with oil of cloves and balsam. If the mass is too hard, it can be softened to any degree by laying it in water. It is far better, however, to let it lie before cutting for a day in oil of cloves (or turpentine), where it becomes transparent as amber, but at the same time a little softer, though still hard enough to be fixed in the microtome.

The imbedding substance appears under the microscope either perfectly homogeneous or in the worst case very finely granulated.

The advantages of this method are that complete series of sections can be permanently produced without much loss of time, and without the different parts of the object being removed from their position, whilst the transparency allows of uninterrupted observation of the position of the object. Moreover, the object need not be so carefully hardened as is required in paraffin. The method is strongly recommended for calcareous and siliceous sponges as well as for worms and the embryos of fowls.*

New American Journal of Microscopy.-Professor Romyn Hitchcock, of New York, announces that it is intended to issue, under his editorship, a quarterly journal, with the title of the American Quarterly Microscopical Journal.' It is to contain, "besides original articles from prominent writers, reprints and translations of the most important papers found in current English, French, and German publications, the Transactions of the New York Microscopical Society, and a complete synopsis of all microscopical matters; and to this end abstracts will be given of every article published during each quarter to which the editor has access, or where abstracts are inadmissible, titles of the papers will be given." The journal is to be "absolutely independent of any business enterprise, and published entirely in the interests of microscopical science."

Anaerobiosis of Micro-Organisms.-The following note by M. Gunning was read at the French Academy on 1st July:-At the meeting of the Academy of Sciences of Amsterdam of the 29th April, 1877, I pointed out that ferrous ferrocyanide was a reagent very sensible to oxygen, and demonstrated by this means that the apparatus and media ordinarily in use for the culture of micro-organisms could not be exempt from oxygen by the methods recommended for that end.

These observations threw a legitimate doubt on the experiments on which the doctrine of anaerobiosis is based, and I have naturally been led to repeat these experiments under conditions which allow this new point of view to be taken account of. Admitting the practical impossibility of obtaining spaces where the absolute absence of oxygen could be proved, I have used glass flasks hermetically sealed, in

*Prof. Selenka, in Zoologischer Anzeiger,' vol. i. p. 130.

which as large quantities as possible of putrescible matter were placed in contact with the smallest possible quantities of oxygen.

The matters which I made use of, viz. urine, blood, soup, yeast, and milk, as well as water and raw meat, and grains of rice, beans, peas, pieces of coagulated albumen, &c., taken in a fresh state, were infected by bacteria taken from similar matters in a state of full putrefaction. The flasks were then sealed and exposed to a temperature of 38-40 degrees; putrefaction was immediately established, to be definitely arrested, however, in all the flasks after a longer or shorter period, often very short, but always sensibly proportional to the quantity of oxygen which was supposed to be present. I have had in my possession for nearly two years a considerable number of these flasks whose contents have lost little or nothing of their primitive freshness.

The details of these experiments are related in a memoir which has been published in the Annals of the Academy of Sciences, Amsterdam,' vol. xii., 1878, and in the sixth part for the year 1878 of the 'Journal of Practical Chemistry,' as well as the arguments which led me to attribute the cessation of the putrefaction solely to the death of the bacteria caused by the absence of free oxygen.

I will ask permission to cite here one of these arguments, because it relates especially to a subject which has often occupied this Academy.

When the flasks containing the putrescible matters terminate in tubes provided with cotton-wool, or are re-curved many times upon themselves, and whose tapered points are hermetically sealed, we are able at any given moment by breaking the point to expose the contents anew to the contact of the air, deprived of germs. If to establish this contact we wait for the moment when the contents have arrived at a state of complete inertia, we observe that the air no longer produces the least phenomenon of putrefaction or appreciable alteration. This proves in my opinion not only that the bacteria as well as their germs are really dead, but also that the organic matters are not susceptible of spontaneously producing others. These experiments are then, as it seems to me, very strong arguments against archebiosis, and so much the more that the organic matters are not subjected here to any other manipulation than the seclusion during several days or weeks of the air-a manipulation which produces no alteration either in colour, structure, or solubility, and which seems to preserve them as much as possible in their natural state.

This is why I have applied this method to the well-known experiments of M. Bastian with urine neutralized by potash; my procedure was the same as his, with this difference, that no measures were taken to sterilize the matter operated on; on the contrary, it was mixed with a drop of urine in full putrefaction. A certain number of flasks of about 500 cubic centimetres capacity were filled as completely as possible with this prepared urine, then sealed and exposed to a temperature of 40°. The urine got thick, but became perfectly limpid again at the end of some days; it then remained in this state without change of colour and without presenting any other sign of

alteration. Other flasks arranged in the same manner, but whose tapered necks terminated in orifices of different size, allowed me to observe not only that the putrefaction was clearly established, but that its intensity was sensibly proportional to the quantity of air which could enter. It was easy in this way to set up putrefaction at all degrees, from zero to the maximum, in different portions of the same matter eminently putrescible and infected, whose conditions of existence presented no other difference than that of the greater or less free access of air.

Urine neutralized by potash must be considered a matter eminently fit for the life of micro-organisms, and extremely difficult to sterilize by the ordinary methods; but from the moment when the organisms which it contains no longer find oxygen, they lose completely the faculty of supporting the bacteria, and with greater reason the faculty of producing others.

The seclusion of oxygen offers a simple means, generally applicable and efficacious, for sterilizing organic matters, and furnishes the most conclusive proofs against spontaneous generation.

M. Pasteur, after the above communication had been read, made the following remarks:-It is seventeen years since I published the first facts relative to life without air or anaerobiosis; since this time I have occupied myself with the cause of error which the author refers to in the preceding note, and notwithstanding the very great precision, as I think, of my first experiments, I have always endeavoured since then to make this precision more perfect. Very recently, on the occasion of the remarks which I published in conjunction with Messrs. Joubert and Chamberland, we carried still further the investigation of the means proper for eliminating in a complete manner the air from our flasks. With this end we combined the action of the vacuum of the mercury air-pump with the properties of white indigo, a substance so well known for its effect in the absorption of oxygen since the work of M. Dumas on the subject.

If the author of the preceding note will go further in his observation, if he will remark, as he does not seem to have done, that putrefaction is often arrested not by the death of the microscopic organisms, but because they have passed to the state of germs, I do not doubt but that he will be led, as was the case with Dr. Brefeld in regard to the development of alcoholic yeast, to retract his assertions, and to recognize that the existence of anaerobic beings rests on irrefutable proofs.

In the second part of his note M. Gunning combats the conclusion of Dr. Bastian on spontaneous generation, and I am glad of the confirmation which he brings to the arguments which I have already used against the latter gentleman.

Haliphysema Tumanowiczii, not a Sponge.-In the July number of the Annals of Nat. Hist.,' Mr. W. Saville Kent records the results of an examination he has made at Jersey of some specimens of this organism found on the fronds and root-stalk of Maugeria sanguinea, in regard to which so much controversy has arisen.

Prior to the discovery of the living specimens, Mr. Kent had