even less truly conical; each consists of a conical or rather globular head, a long central filamentous portion, and a proximal spindle-shaped portion. There is no cornea in either the lateral or the frontal eye, but the distal end of each cone comes into relation at the surface with a double cell, containing two (Semper's) nuclei. These double cells do not fit closely to one another, but leave triangular interspaces: the boundary wall between the two halves of which they are composed penetrates into a very evident cleft, marking the division of the cone into two longitudinal segments. Schmidt's observations give no support to Pagenstecher's view that this separation of the cone into two longitudinal moieties is an evidence of multiplication by division.

But perhaps the most important observation on these cones is that in hardly a single case is the axis of the visual rod at right angles to the external or corneal surface, so that Müller's theory of mosaic vision is here quite inapplicable, since there is neither the straightness of the refracting bodies, nor the contrivance for absorption of lateral rays required by that view of the action of the socalled compound eye. The author considers that the eyes of Phronima are mere makeshifts for image-forming organs, and that they serve only to distinguish different degrees of light and colour.

Observations on the visual rods of other Crustacca showed that in Palomon many of the cones are straight, but that those at the periphery of the organ are oblique to the corneal facets, their proximal segments being strongly bent. In Palinurus this flexure sometimes amounts to 90°. In the lobster the rods are very irregular, hardly two being alike their proximal segments show the greatest amount of variability as to size and degree of flexures, and have no resemblance at all to image-forming bodies.

The only insect examined by the author is Dytiscus marginalis; in it, as in the prawn, he finds that the rods towards the periphery of the eyes exhibit a marked flexure. The paper is accompanied by a plate.

Poison Glands of the Centipedes. It has long been known that the Chilopod Myriapoda, commonly known as centipedes, which are carnivorous in their habits, kill their prey by a poison injected at the first bite of their formidable nippers. The seat of the glands secreting the poisonous fluid was, however, unknown, the organs formerly supposed to secrete the venom being found to pour their secretion into the cavity of the mouth and not into the nippers. Mr. McLeod, during a residence in Java, examined some of the large centipedes with which that island abounds, and especially Scolopendra horrida, and finding the glands which might easily be taken for poison glands had nothing to do with the nippers, which nevertheless always exhibited a very distinct orifice at the tip, he was led to search for the glands in the interior of those organs themselves.

The process he adopted is one that has of late given admirable results in the investigation of the anatomy of many animals; namely, the preparation of sections of them in various directions, after they had been immersed in melted paraffin, the subsequent hardening of which keeps all parts in their natural positions during the operation of cutting. By this means he detected the poison gland, which is

situated partly in the actual biting portion of the nipper and partly in the broad basal joint which supports the latter. The glandular apparatus consists of a chitinous duct leading to the orifice at the apex of the organ, and forming the axis of the gland. It is perforated in its course by a multitude of small apertures, each of which leads into a minute cylindrical tube, terminating in a long secreting cell, the whole mass of these cells being arranged in a radiating fashion around the duct. The entire organ is surrounded by a membrane, and has the general form of a four-sided prism. Notwithstanding its comparatively small size, Mr. McLeod has detected the same arrangement in Lithobius forficatus, the common European centipede.*

Microbia. Under the title of "The Influence of M. Pasteur's Discoveries on the Progress of Surgery," M. Sédillot contributes a paper to the French Academy,† which he commences by pointing out that the microscopical organisms pervading the atmosphere (which Pasteur has shown are the cause of the fermentations attributed to the air, which is merely their vehicle), form a world by themselves, the history of which, as yet in its infancy, has already proved fertile in conjectures, and in results of the highest importance.

The names of these organisms are, however, very numerous :Microzoaria, Microphyta, Aerobia, Anaerobia, Microgerms, Micrococci, Microzymes, Bacteria, Bacteridia, Vibrions, Microderms, Confervæ, Ferments, Monads, Animalcules, Corpuscles, Torulæ, Penicillium, Aspergillus, Infusoria, Leptothrix, Leptotrichum, Spores of Achorion, of Favus, of Oidium, of thrush, Organisms of right and left tartaric acid, septic and septicemic Zymes, &c., terms which need to be defined and partly reformed. The word Microbia (from mikros, small, and bios, life) has the advantage of being shorter and of a more general signification, and of being approved by M. Littré, the most competent linguist in France; and the author therefore proposes it for general acceptance, without, however, laying aside altogether those terms in use to designate varieties which have been more particularly examined. M. Pasteur also approves of the term.

The paper proceeds to discuss the changes in surgery which were brought about by the proof of the existence of Microbia, and "which threw a vivid light on the obscurity and false conceptions in which surgery had gone astray. From the highest antiquity medical science took notice of the preponderating influence of the air on health and disease; but, in spite of the immense progress of science, time brought about no change in this point of view until the discoveries of M. Pasteur essentially modified the position of surgery and the treatment of wounds in particular. Surgeons were divided by different doctrines, reducible to a single one having for its basis 'the dangers of contact with air.' All were founded on observations which were exact and approached to truth, without, however, attaining it by reason of false interpretations and hasty generalizations. The discoveries of M. Pasteur at once reconciled the apparent contradictions, and explained the *Bull. Acad. Roy. de Belgique,' vol. xlv. 'Pop. Sc. Rev.,' N. S., vol. iii. Comptes Rendus,' vol. lxxxvi. p. 634.

p. 111.

use, in the treatment of wounds, of pulverulents, styptics, balms, ointments, caustics, camphor, iodine, alcohol, and a hundred other antiseptic substances which act as barriers to the contact of Microbia, or as agents of their destruction. Herein lies the principle of all preservative and curative treatment. Medicine and hygiene is applied to the destruction of the Microbia, external and internal, and to augment the vital resisting power of the patient.

The cultivation in fluids of Cohn, Raulin, and Pasteur has shown that certain species of Microbia (Aspergillus niger amongst others) have never been found amongst the preparations impregnated by the passage of a given quantity of air. Yet to procure this cryptogam it suffices to expose a slice of moist bread to the air, when they are soon seen to grow. This fact fully explains the variety of accidents to which wounds may be subject by reason of the numberless modifying circumstances which render them more or less amenable to the development and increase of different Microbia." It would be very desirable, he thinks, "to set up apparatus for analyzing the air in hospitals by which the degree of salubrity or infection would be daily determined."

Orchella as a Staining Material. Dr. C. Wedl, of Vienna, describes the following process of staining animal tissues, in Virchow's Archiv für Pathologische Anatomie,' vol. lxxiv. p. 143. The so-called French Orchella-extract, from which the excess of ammonia has been extracted by gentle warming in a sand-bath, is poured into a mixture of 20 c. cm. absolute alcohol, 5 c. cm. concentrated acetic acid (of 1.070 spec. grav.), and 40 c. cm. distilled water, till a saturated dark-red stain is obtained, which must then be once or twice filtered. After the section has been hardened in Muller's fluid and spirits of wine or chromic acid, it is washed with distilled water. The latter is then got rid of by means of blottingpaper, and some drops of the staining fluid are applied to the section. The stain is taken up immediately by the protoplasm of the cells, whilst nuclei and nucleoli are not coloured. Horny or calcareous epithelial formations likewise take no stain. Connective-tissue cells are very deeply coloured, whilst the fibrillated intercellular substance of the connective tissue takes less of the stain. The basic substance of bones and that of the teeth take the stain, also the ganglion-cells with their prolongations. Fresh pathological formations also give sharp images when coloured with orchella. As medium the author used levulose.*

Construction of Eye-pieces.-In consequence of the discrepancies in published statements in regard to eye-pieces, Mr. W. H. Seaman, of Washington, has made a full series of measurements of the parts of eighteen eye-pieces by English and Continental makers. As the result of these measurements (which were laid before the Indianapolis Congress †), it was found that the common ratio between the focal lengths of eye-lens and field-lens was, in one instance it was, and * Zeitschrift für Mikroskopie,' vol. i. p. 318. American Naturalist,' vol. xii. p. 838.

in one of older construction. "The only general principle in regard to the interval separating the lenses is, that it shall be less than the solar focus of the field-lens; and when in the deeper eye-pieces and those which are orthoscopic it seems to exceed this limit, it must be remembered that in connection with the objective the eye-piece receives diverging rays, and for such its focus is beyond the solar focus. It may also be noticed that but a small part of the diameter of the eye-lens is actually used in the lower powers."

Malpighian Vessels of Insects.-Dr. E. Schindler has published an account, with three plates and a woodcut, of his extended researches on these structures.* This paper gives, first, an general account of the structure of the vessels in question, then an historical summary of the work of former observers, then a special account of the Malpighian vessels in the various groups of insects, and finally some concluding remarks, summarizing the results at which he has arrived. It is only possible here to give some account of the first and last of these sections.

The Malpighian vessels consist of at least three layers: externally a serous coat of nucleated connective tissue, then a delicate homogeneous tunica propria, and finally a single layer of glandular epithelial cells bounding the lumen of the tube. To these is sometimes added a perforated cuticular tunica intima. Elastic and muscular layers are but little developed, and the flow of the secretion, set free by the dehiscence of the gland-cells, is produced partly by its own gradual accumulation, partly by the movements of the other organs. The tubes may appear white, yellow, brown, green, or red, according to the colour and quantity of their contents. Their size and number vary greatly, their length being, as a rule, inversely proportional to their number.

The Malpighian vessels are exclusively excretory (renal) organs, and not, as has been supposed, biliary, or both biliary and renal. This is supported by their mode of development as outgrowths of the hind-gut by their early origin, and by the fact that they are functional before any bile is found and while the hind-gut is still a blind pouch, but chiefly by their close resemblance to the urinary tubules of higher animals, and by the nature of their contents. It is well made out that they contain specific urine-constituents, such as uric acid, acid sodic and ammonic urates, leucin, calcic oxalate, &c., and that no substance not already known in the urine of other animals occurs in them.

The chief facts tending to support the theory that these tubes are hepatic as well as renal, are the yellow and green colours often observed in them, and the polymorphism of their epithelial cells. With regard to the first of these points, Schindler states that the colour is dependent on a specific colouring matter in the blood plasma, that no bile pigments are present, and that the colour is very inconstant. The polymorphism of the cells was used as an argument for double function by Leydig, who supposed that certain cells had assigned to them a hepatic, others a renal function. But according

* Zeitsch. f. wiss. Zool.,' vol. xxx. p. 587.

to Schindler there is no constancy in the occurrence of the different forms of cells, and moreover all of them contain the characteristic urinary concretions.

The urinary epithelium of insects contains none of the so-called Dauer-zellen or long-lived cells, but renewal of the cells takes place either by division, or (probably) by the nucleus of a cell which has undergone dehiscence, enlarging to form a new cell, its nucleolus becoming the nucleus of the latter.

Parasitic Crustacea.-M. Hesse gives the name of Pachynesthus violaceus and Polyoon luteum to two new parasitic crustaceans of microscopic dimensions (1-2 mm.), two females of which were discovered in the harbour at Brest, enclosed in the interior of a compound ascidian. The genera are new. M. Hesse remarks * in regard to their life-history:

The completely stationary and so to speak secluded existence, to which these crustacea are condemned, does not require, as in the case of those which live in a free condition, perfect means of locomotion, for which they would have no use; those which they do possess are rather destined to serve for creeping than swimming.

Constantly shut up in an extremely limited enclosure formed of a more or less hard test of cellulose, they are obliged, in order to move in these narrow dwellings, to make themselves a passage by main force, and as Professor Giard has very well observed in his remarkable work on Synascidia, they are obliged to make galleries, by means of which they introduce themselves into the viscera; they penetrate into the ovaries, and produce such disorders as often cause the death of the whole colony, and might lead to the belief in the existence of a new species, although these modifications are only the result of the disturbances which they have produced in the individuals.

This work of burrowing, which I will compare to that of the mole cricket, results in the disappearance of the common cloaca and their replacement by small openings very near together, the utility of which to these crustacea is easily conceived. Without these issues, in fact, the young embryos could not quit the enclosure nor disseminate themselves, and thus contribute to the dispersion of their species, and the males would be imprisoned and reduced to a state of captivity which is evidently contrary to the role which they have to fulfil, if I judge from crustacea closely allied to these, with which I am acquainted, and which are extremely agile and provided with all necessary means of swimming with facility.

Moreover, this liberty which the males enjoy easily explains their rarity, or rather the difficulty which there is in procuring them. They are rarely sedentary. It is of course on this account that they are more seldom met with than the females, which are condemned to live always in confinement. These latter are besides rather difficult to see, by reason of their extreme smallness; and if it were not for the eggs, which are generally of a very marked colour and which denote their presence, they would often not be seen.

The means of locomotion with which these crustacea are endowed

* Ann. des Sci. Nat. Zool.,' Cth ser., vol. vii. p. 7.