It must not be lost sight of, that amongst some fifty insects found on the two ears, we can scarcely suppose some of them should not be mature, if they belonged to the family of Acarea. This view led me to seek carefully for some ova beneath the skin, or the shells attached to the hairs; yet nothing was found beyond portions of the inflammatory exudation carried up by the young hairs, or adherent where the hairs had touched the irritated surfaces; nor was any trace of an ovum found in the bodies of those cut open or crushed under the dissecting microscope; though in the mass of granular matter, four small nuclear-looking and granular masses, larger and more firm than the rest of the large granules, were found, two on opposite sides of the lower half of the abdomen, but what they were it was impossible to say correctly. If the foregoing view be correct, amongst some of the ova we may expect the male to be reproduced. Again, we have no evidence they were not, in the full sense of the word, adventitious just passing one part of their lives in a luxurious feast; yet, if they belong to the Ixodeæ, may we not suppose either that one or more females attached themselves to the bat, and then gave birth to the colonies, for they are described as depositing or producing by a continuous pont of many days, upwards of a thousand glutinous eggs (?). Yet the gestative state of the Ixodes is said to be continued by the insect detaching itself and falling to the ground for completion; so this hardly admits of its performance on the bat.

The singularly peculiar, if not almost unique character of the generative act of the Ixodidæ, described by Professor Gené, of Milan, and translated in abstract by Mr. A. Tulk, in the Annals and Magazine of Natural History,' vol. xviii., to which I beg reference for those interested in the history of these minute creatures, and which will amply repay a perusal, I can only in part quote here. In brief it may be stated, the male inserts its rostrum into the orifice, situated upon the middle of the sternum, between the coxæ of the last pair of legs. Mr. Tulk points out the "very striking relation, if only approximative in kind, between the organ employed by the male Ixodes to copulate with the female, and the palpí as ministering to similar uses in the Araneides, or true spiders.' That the female afterwards depresses upon the sternum all the palpi that compose the rostrum, when there is seen to be "protruded from the duo-cephalic plate, a turgid vesicle," terminated by two lobes, "vesica biloba," having at the apex a most minute aperture. "When this organ has been well dilated, so as to pass beyond the rostral palpi, the animal erects the pectoral canal, and gives exit to the oviduct," and "proceeds at once to disemburden itself, between the lobes of the vesica. This clasps, compresses, and appears as if sucking the oviduct for a few seconds; but often the oviduct is retracted, and re-enters the sternum, leaving an egg

between the lobes of the vesicle, which clasps it firmly, turning it to and fro in all directions, and vibrating now and then in a spasmodic manner. Four or five minutes having elapsed, during which time the ovum remains between its lobes, the vesicle disappears by re-entering its internal situation. The ovum is left upon the inferior labrum, and this being elevated, along with all the palpi that compose the rostrum, thrusts the ovum upon the duo-cephalic plate, or in front of the body-these acts being renewed for as many ova as the female may have to discharge. A series of very interesting experiments made by Professor Gené are then related, bearing upon the correctness of the foregoing.

Before drawing this lengthy article to a conclusion, it is necessary not to omit noticing that the parasites of the bat's ear prefer the inner surface, where the hairs are fewest and the glands most numerous. They collect in companies (vide Fig. 1, where twenty are seen, and seven apertures made through the dermis left by the detached insects). This figure represents a very hungry lot, and they generally, so far as could be judged, seek those parts of the inner surface of the ear that are well provided with nerves; a nerve bundle is shown at * Moreover, they appear to prefer to use the aperture through which the hair protrudes, than to be at the trouble of tearing one open. They seem to fix themselves much in the same way as the tick to one spot, and by their presence cause a considerable amount of mischief, inducing much congestion and thickening of the tissues beneath. Two such apertures are represented more highly magnified at Fig. 8, one having a minute hole at; the other, ***, showed no such opening. The hair follicle and sebaceous glands appear totally destroyed in most of the openings; the cartilaginous tissue seemed to suffer only slightly; the vessels looked enlarged; a large nerve bundle is In these examinations the skin was dissected off both sides of the cartilage, to obtain the necessary transparency; portions were subjected to various reagents, and showed that the ear of the bat seems almost in its amount of nerves, &c., to rival its wing, described in abstract in the June number of the Society's Journal, p. 272, from Dr. Joseph Schöbl's most interesting observations. However, it would be only in recent and injected specimens any attempt could be satisfactorily made in the examination. of these organs. The incompleteness of this paper is regretted, but it is hoped sufficient has been stated to induce other observers, when opportunity offers, to give us the benefits of a more extended examination.

seen at

V.-Note on the Resolution of Amphipleura pellucida by a Tolles's Immersion th.

By Assistant-Surgeon J. J. WOODWARD, U. S. Army.

IN my paper on the use of the Nobert's plate, written in April last, and published in the July number of this Journal, I found myself compelled to make a few remarks on the objectives of Mr. Tolles, of Boston. While complimenting this maker on his excellent workmanship, I felt constrained to say that I had not found that his objectives excelled those of like powers by other first-class makers.

Late in June of the present year, however, I received from Mr. Tolles a th, the performance of which is so remarkable that I take pleasure in drawing attention to it.

This objective is so made as to work either dry or immersion, and it is of its performance when used wet that I desire to speak. Its magnifying power at 48 inches distance between micrometer and screen (without an eye-piece) is 250 diameters when corrected for immersion uncovered, 275 diameters when corrected for the thickest cover through which it will work. It is therefore of rather higher power than a 1th, but less than a th.

Now, with this objective I find no difficulty in resolving Amphipleura pellucida, the objective successfully displaying the transverse striæ on all but the most minute and difficult frustules.

To illustrate the character of the performance, I send you herewith two positives on glass from negatives taken by this th.*

It is

The first shows two frustules magnified 256 diameters. of course necessary to use a lens, or a low power of the compound microscope, to see the striæ, which will be found to be quite sharp.

The second shows the same two frustules magnified 920 diameters. The striæ can be seen with the naked eye, still better with a lens.

I send no paper prints of these negatives, because, on account of the fineness of the striæ, as seen with the above powers, they would not be satisfactory.

I add, however, a third positive, representing the same frustules magnified 1140 diameters by the immersion th of Powell and Lealand.

This picture certainly shows that the new th cannot be claimed to supersede the highest powers at present in use, yet nevertheless is not, in my opinion, injurious to the 4th, for it must be mentioned that the immersionth of Powell and Lealand, with which this picture was taken, magnifies at 48 inches distance, without an eye

The photographs are admirable. They are at the Society's rooms, where they may be seen.-ED. M. M. J.'

piece, 900 diameters when used uncovered, and 1100 when used covered; and it is certainly highly creditable to an objective of so much lower power to be capable of resolving so difficult a test as the Amphipleura.

From this performance I expected that the new th would at least resolve the sixteenth band of the Nobert's plate; but in this I have hitherto been unsuccessful, getting indeed handsomely through the fifteenth band with it, but no further. Now, as the objective resolved Amphipleura frustules with striæ as fine as 96 to the Tooth of an inch, I can only account for this circumstance by supposing a greater difficulty in the case of striæ of equal fineness on the plate, as compared with Amphipleura. This circumstance, which had previously escaped my notice, I have since confirmed by comparison with a number of different objectives.

În conclusion, I beg you to show the photograph accompanying this note to any of your readers who may take an interest in the performance of objectives of moderate power. I should be very happy to hear from them how this result compares with the work of the best modern English ths, particularly as I have access at present to no English glass of this power constructed within the last two years.

VI.—Micro-ruling on Glass and Steel. By JOHN F. STANISTREET, F.R.A.S. With Illustrative Remarks by HENRY J. SLACK, F.G.S., Sec. R.M.S.

PLATE XCVII.

By the kindness of John F. Stanistreet, Esq., F.R.A.S., of Liverpool, I have lately been able to examine some very beautiful specimens of ruling on glass, and also on steel, executed by him with a machine of his own contrivance and making, of which some particulars are subjoined.

The first specimen which I received was a star exquisitely ruled on a small circle of covering glass (1" diameter), and it cannot be better described than in Mr. Stanistreet's own words :-" The mounted disk, which I herewith enclose, has a star of 50 rays, or bands of lines, placed radially, each band consisting of 26 lines ruled parallel and equidistant, the zoooth of an inch apart. The star therefore contains 1300 of such lines. The lines are pur

posely scored very strongly to increase the intensity of the diffraction spectra, as I find that lines very much finer and closer (which are just as easy to rule up to about 10,000 to an inch) are not so effective for this purpose.

Some beautiful diffraction spectra can be obtained with this star,

VOL. VI.

M

but to the microscopist it is instructive from the various perspective appearances it presents. From the principle on which it is ruled the lines composing each ray proceed for some distance before coming in contact with the lines belonging to adjacent rays, as shown in Fig. 1, Pl. XCVII. Each ray, at its peripheral end, commences with what looks like a sharply-cut dot, the first impact of the diamond point with the glass, and the lines composing each ray gradually diminish in length, giving the wedge-shape shown in the figure. When the star is viewed with a low power (say 3"), with dark-ground illumination, the optical effect of the rows of bright dots, with which the lines commence, is to suggest that each ray stands up from the general plane of the glass, that all look like a number of spokes of a fan placed, more or less, vertically on the table. A higher power (rds) makes this more striking, as in Fig. 2. The position of each ray, with reference to the angle at which a light strikes it, determines how much it slopes either right or left of the vertical plane, and one or two rays will appear nearly in that plane. Keeping the illuminating apparatus stationary, and revolving the stage, causes the apparent slope of each ray to vary, and if any pair of rays be selected for particular observation, they will be seen to undergo curious apparent changes of position. At one point of the stage rotation it will appear as if the eye beheld the outside of one ray and the inside of its neighbour, while at another point the appearance will be reversed, and it will look as if the outside of the first and the inside of the second had come into view. If the object is then moved so that the wedgeshaped ends of the rays are thrown out of field, the eye is somewhat tempted to consider adjacent rays as not quite in the same plane, but the striking illusion just described has disappeared.

After proceeding separately for some distance, the rays commence their contact, and the intersections of the several lines composing them produce a secondary star, with finely-pointed rays, gradually broadening towards their bases. It is easy to illuminate these secondary rays so as to make this star appear in a plane higher than that of the primary star, and to give an appearance of solidity to each ray.

Near the centre of the star, where the rays meet, the aspect is beautifully watered and the lustre is silvery, or delicately iridescent, according to the illumination. In the centre is a clear space, and this has the aspect of a deep hole, an appearance much assisted by the curvature of the lines as they come to the point.

The appearance of concentric scorings seen on the secondary star arises from intersections. It is striking with powers under inch, but with inch and upwards they grow fainter, and disappear in a conflict of cuts.

Not to enlarge further on this particular star, it will be seen