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ever, been mounted for sale, but they well merit attention; and though on close examination their markings are found to be similar to those on the test scale, omitting all consideration of the

and many died. I therefore liberated those remaining in the cellar whence their parents were obtained, lest the species should be exterminated. I have tried several times since, without success, to keep this species in confinement: they always pine away and die; and though they will eat oatmeal, they do so but sparingly.

The progeny of both kinds of Podura were very numerous in their native haunts on the 1st of October. Possibly the dampness of the past summer had promoted their increase. In several places the under sides of certain boards swarmed with the black species, and their exuvia were equally abundant in the same situations.

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Fig. 46. White Podura (Lepidocyrtus Albinos?).

I have lately noticed another Podura-pearlywhite in colour, with red eyes, small, having rather long antennæ, and furnished besides with long hairs somewhat like the speckled. I am told its name is Lepidocyrtus Albinos, and that it is the smallest

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Fig. 45. Scale of Speckled Podura, by reflected light, small side; condensing lens, objective, C eyepiece.

About the 6th of June nine of these insects were inclosed in a cell, and on the 16th I noticed that about sixty globular eggs were laid. On the 24th of the same month, the eyes of the contained young might be perceived through the shells, which burst on the 27th, and permitted the young to make their exit.

These are lively from the first, and resemble their parents in all, saving that they appear to be very delicate and destitute of scales.

While the young of the black Poduræ seemed to be quite comfortable in the damp cell, these appeared soon after to be in an unhealthy condition,

Fig. 47. Scale of White Podura; objective, A eyepiece. of the scale-bearing Poduræ. It seems to be very partial to the vicinity of flower-pots, and underneath them it may often be found. One specimen was damaged in being captured, two of the joints of one antenna being broken; but in the course of ten days the damage was repaired, and the one antenna was almost the counterpart of the other. The scales, which were first described to me by the late lamented Mr. Richard Beck, are very thin; but notwithstanding this the markings are very

distinct, and have a great tendency to follow each other in longitudinal rows. In order to give a rough idea of their appearance comparatively with others we attach a figure, exhibiting them as seen under an 4th object-glass. In Mr. Beck's beautiful paper in the Microscopical Journal, on the subject of

well with a good half-inch objective, assisted by the condenser and a deep eyepiece; but, although they are said to be visible with a one-inch, it is only, to quote from Dickens, when you "make believe very much" that the mottlings then seen are comfortably resolved.

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Fig. 48. Test Podura Scale; upper portion, objective, A eyepiece; lower portion, objective, C eyepiece. the Scale of Lepidocyrtus, he says: "The best scales are obtained from the insects found in comparatively dry places." So far, and in some other particulars, I find our experiences agree. His speciality (which we figure as the "test scale") is either a variety of the black Podura or a distinct species; most probably the latter. The outlines of Podura scales are very different in different species; and although there are many erratic shapes, those drawn will, we think, be found to be the forms which predominate. The drawings of the scales have all been made with the aid of Ross or Beck's object-glasses and Powell and Lealand's achromatic condenser (170°). The markings can be seen without an achromatic condenser; but the view is infinitely more satisfactory when this apparatus is used. I have also employed Smith and Beck's, which is admirably adapted for exhibiting them. A moderate aperture only is requisite, both in the object-glass and the illuminating apparatus, for their perfect display; but the workmanship of the objective must be of the best description. Any error in the correction of the lenses, whether in the manufacture or in their adjustment for penetrating the thin covering glass, is immediately betrayed by the peculiar appearance which the markings present. Mr. R. Beck has dealt with this subject so thoroughly in the paper I have alluded to, that I hardly feel competent to speak on it.* I have seen the markings moderately

I refer more particularly to the accepted standard test scale.

Fig. 49. Scale of Speckled Podura, oblique illumination.

An object-glass, which will show the Podura scale perfectly, may be predicted to be capable of being employed satisfactorily on the easier diatoms, such as P. angulata and P. hippocampus; but it does not follow that another glass, which will show the striæ on the N. rhomboides, Surirella, P. fasciola, N. cuspidata, &c., will perform equally well on the Podura scale. It is possible, however, for a good high-power glass to be equal to both these require

ments. Amateur mounters should cover the scales they put up with the thinnest possible glass, so that, when opportunity offers for an examination of the slide under a remarkably good th or th, they may not find themselves doomed to disappointment, owing to the inability of the objective to penetrate the thick cover.

In conclusion I beg to offer a few remarks on the scale of the Speckled Podura. As I have stated above, it possesses transverse striæ, and these are rendered most distinct when the central rays of the achromatic condenser are stopped out. I believe that the structure of Podura scales in general may be best studied in this one. From very careful examinations I have no doubt, that the

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all other insects. This is best shown by oblique illumination; but when the illuminating ray is in a direction corresponding to the axis of the microscope the appearance is totally changed, and the wedge-shaped markings, which I believe to be hollows between the pleats or corrugations (and not particles, as stated in the "Micrographic Dictionary" and elsewhere), come into view directly. Their dark outlines, I think, represent the shelving sides of the little pits, and the bright space in the centre of each is the deepest portion, which from its position with regard to the ray, obstructs the least amount of light.

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By moving the diaphragms of Powell's condenser a little backwards and forwards, so as to obtain alternately direct and oblique light, the appearances represented in the figure attached are given. The conclusion I have arrived at seems still further supported, if one of the most strongly-marked scales be examined with a 4th objective, and Smith and Beck's patent illuminator for opaque objects under high powers. The wedge-shaped markings are then distinctly seen to be little pits.

During the month of October last, as I was ascending one of the rising slopes of the Cotteswold hills, in the vicinity of Cheltenham, I thought I perceived the peculiar but agreeable scent of Russian leather, and recollecting that there was a fungus reputed to possess that odour, I immediately directed my search for it. Several specimens were growing around me where I stood, and thus I had been led to detect this little white fungus by its scent, as we sometimes do the violet in the spring of the year, before the eye reveals its whereabouts.

Opaque illumination by means of the side-condensing lens and ath object-glass shows the tops of the ridges of pleats illuminated, and the spaces between in very strong shadow, provided the beam of light strike the scale sideways. If it strike lengthways, the view is too indistinct to be satisfactory. My opinion on the subject differs slightly from that of Mr. Beck, who regards the wedgeshaped markings as elevations, and argues accordingly. The question as to whether they are hollows or elevations is of no great importance, and it is exceedingly difficult of resolution. Mr. Beck's remarks refer to the test scale.

S. J. MCINTIRE.

The Rev. M. J. Berkeley says of this species (Hygrophorus Russo-coriaceus), that it is rare; but I have a suspicion that it may have been overlooked as the young, or a small state of Hygrophorus virgineus, which at a distance it somewhat resembles. It may, however, be readily known from that species by its delightful scent alone, which it retains after drying, and to such an extent, that I think it might be made available for the scenting of drawers, &c.

In the same pasture I gathered Hygrophorus murinaceus, which possesses the odour of aquafortis -far less agreeable, but perhaps equally remarkable. The collector of the larger fungi is frequently reminded of this singular similarity of odour to a series of odd things, both of a disgusting and agreeable nature, as the following brief enumeration will illustrate, viz., cinnamon, garlic, heliotrope, cucumber, gas-tar, tarragon, new flour, mice, bugs, ripe apricot, putrid flesh, &c. The similarity of form and colour which some insects bear to portions of the vegetable kingdom, would lead one to suppose that they were designed to protect them from wholesale destruction by birds, &c.; but as regards the odour of fungi, it seems more difficult to form an opinion. The mycologist, however, often finds that they serve him as valuable aids in the determination of species, and without which, his conclusions might be more exposed to error. H. BEACH.

MARKS.-A delta is a water-mark; a round crater a fire-mark; and every force which acts on a surface makes a tool-mark which may be learned. Each mark is like a letter. It has a form and a meaning, but only for those who learn to read.-Frost and Fire.

THE WASP'S STING, ITS POISON GLAND.

SPIROGYRA.

THE discussion relative to the fang and poison THE various species of Spirogyra are found,

gland of the spider, which has appeared, from time to time, in the pages of SCIENCE-GOSSIP, and in which I have taken a part, has led me to examine the stings of bees and wasps, with a view to satisfy myself as to their structure, and to observe what similarity there might be between them and the fangs of spiders, especially in reference to their poison glands. Accordingly, I cut out the sting of a wasp with all its attachments, in as unbroken a state as possible. I spread out the whole on a glass slide, and washed the parts with lukewarm water, without using liquor potassæ. I then allowed the water to evaporate gradually, and the sting, &c., to become quite dry on the slide; and finally, having moistened the object with turpentine, I mounted it in balsam.

I found that in wasps, as in spiders (SCIENCEGOSSIP, for 1866, page 229), the poison gland is attached by a hollow cord of about the length of the gland itself, and that the course of the cord could be traced down the body of the sting. The gland is similar in shape and size to that of the spider, and when examined under the microscope, with ordinary transmitted light, did not exhibit anything remarkable, except that there was a kind of knot in its extreme end, and attached to it, which seemed to be ramified with a structure of tracheæ. Upon examination with polarized light, nothing particular demanded attention, until this knot came in the field of view, when brilliant starlike crystals blazed forth on the dark ground. The crystals were small, each had a dark cross in its centre, and with selenite gave the usual appearance of complementary colours.

If I would indulge in a deduction from the above appearances, I would say, that the gland contained a fluid poison, in which the crystals were in solution, the evaporation of the fluid poison leaving the crystals as observed.

It would be interesting to try whether a similar treatment of the poison glands of the spider would lead to similar results. This I may attend to, on a future occasion, if I be not anticipated by a more diligent observer.

The slide containing the sting and the gland with the crystals, I have in my possession, and I have no objection to lend it for the examination of any reader of SCIENCE-GOSSIP, who may be sceptical, because unable to verify the appearances I have related. Armagh. LEWIS G. MILLS, LL.B.

A LANDSMAN who has only seen a puddle in a storm, has no clear notion of the Atlantic in a gale; and so it is with a man who has never been far from home.-J. F. Campbell.

during the spring and summer, in open exposed pools of water, or in slowly moving streams, and are all remarkable for the beautiful manner in which the bands of chlorophyll are disposed within the cells. They consist of bright green filaments, varying from the hundredth part of an inch to a yard in length, made up of cylindrical cells, joined end to end. Some of these occur in nearly every pool, and appear on the top of the water in green or brownish patches, with bubbles of air entangled in their mass. In streams, they attach themselves to weeds, and the long green filaments, waved to and fro by the current, are very pretty.

When viewed under the microscope, with a power of one or two hundred diameters, the bands of chlorophyll are seen disposed in various elegant spirals. In some species these bands are single, in others there are two, three, or four. Upon these bands, which are generally slightly jagged along their edges, are grains of brighter green, disposed at pretty regular intervals, and adding greatly to the beauty of the plant. Sometimes the larger grains are surrounded with smaller ones, and the bands appear like two festoons of exquisite green flowers (fig. 3).

In some cells, but by no means in all, a nucleus may be seen, clinging to the side of the cell or apparently held in its position by strings of protoplasm (figs. 1, 5). In the terminal cell the rotation of the protoplasm is frequently observable, the current seeming to flow down the middle of the cell, and return by the sides.

A young plant is represented in fig. 6, the whole number of cells in which was 20, but only those at each end and in the middle are represented, in order to show the root-like termination, and the manner in which the spiral bands are gradually developed. In the two lowest cells the chlorophyll appears in a shapeless mass, in the third, the spiral bands begin to be marked, and in the middle of the filament they appear as at b. At the growing point, they are distinctly marked, but somewhat compressed. In the ordinary cells of this specics, the spiral bands, which are rather lax at the ends of the cell, in the middle run close up to one another, and give a peculiar character to the filament.

The cells of different species are not always terminated in the same manner. In some a cell separated from the rest exhibits a rounded outline, in others it is at first slightly constricted, and then rounded (fig. 10). In the former case, the junction of two cells is flat, but in the latter the cell-wall is folded back. This may be readily observed, when the plant is treated with iodine (fig. 10,ƒ).

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