Here is a large specimen, resting with raised hind legs on the ceiling, and now in alarm off with shrill humming flight to the window. I decapitate her without compunction, as it is but a fair penalty for her murderous deeds ; and as, of old, the axeman held up " the head of a traitor " to public gaze, so I lay this head on the glass of the compressorium for your contemplation.

And before I apply pressure to the glass-plate, devote a moment's attention to the head as a whole. First, the head itself is a hemisphere, almost wholly occupied with the two compound eyes, which present the beautiful appearance of a globe of black velvet, studded with gold buttons arranged in lines crossing each other at right angles. The summit of the head, where the two compound eyes unite, bears a sort of rounded pedestal, the area of which forms the sole part of the head not covered by the organs of vision. On this are placed, side by side, the two antennae, springing from rounded bulbous bases; they consist of twelve (exclusive of the basal bulb) cylinclrical joints, which are beset on all sides with short arched hairs, but have besides a whorl of radiating long hairs surrounding the bottom of each joint. The effect of this is exceedingly light and elegant.

Between these projects a long cylinder, which represents the lower lip (labium) ; it slightly swells towards the tip, where it forms a round, nut-like knob, covered with exceedingly minute papilla 1 , and no doubt constituting a highly sensitive organ of touch. For the greatest part of its length it is covered with lined scales, and with short arched hairs like the antennae, while each side of its base is guarded by a labial palp of three joints.

On applying a graduated pressure, slowly increased to actual contact of the plates (or as near an approximation to it as we can effect), we see first that the nut-like tip of the labium expands into two concave leaves, like the bracts of a bud, and displays two pairs of more delicate leaves within them. Then, from a groove along the upper side of the labium spring out several filaments, of great elasticity, and of the most delicate tenuity. One pair of these represent the mandibles ; they consist each of a very narrow blade, with a stronger back like that of a scythe. Their tip is brought to a most acute point, and the edge in immediate proximity to this is cut into about nine teeth, pointing backward ; the rest of the edge is smooth, but the whole blade is crossed by a multitude of oblique lines of great delicacy, which may be intended to keep the edge constantly keen.

Next come the maxillce, or lower jaws, horny filaments as long as the former, but still more delicate, constituting simple cutting lancets, with a back and a keen blade, a little widening at the tip.

Besides these there is the tongue, consisting of a central rod which is distinctly tubular, and of a thin blade on each side, fine-edged and drawn to an acute point. And also the labrum or upper lip, an organ having the same general form, but constituting an imperfect tube ; a tube, that is to say, from which about a third of the periphery is cut away, so as to serve as a sheath for the tongue, which ordinarily lies within its concavity. I scarcely know whether this apparatus is not more wonderfully delicate than any we have examined—even than that of the Flea. And how effective it is you doubtless well know; for when the array of lancets is introduced into the flesh, you are aware that a tumour is left, which, by its smart, itching, and inflammation, causes much distress, and lasts many hours. This effect is probably produced partly by the deep penetration of the instruments—for they are fully onesixth of an inch in length, and they are inserted to their very base—and partly by the injection of a poisonous fluid, intended, as has been conjecturally suggested. to dilute the blood, and make it more readily flow up the capillary tubes. The channel through which this fluid is ejected is probably the tongue, which you see to be permeated by a tube containing a fluid ; and the same channel may afford ingress to the diluted blood.

The labium does not enter the wound. If you have ever had the philosophic patience to watch a gnat while puncturing your hand, you have observed that the knob at the end of the proboscis is applied to the skin, and that then the organ bends with an angle more and more acute,

until at length it forms a double line, being folded on itself, so that the base is brought into close proximity to' the skin. Meanwhile the lancets have all been plunged in, and are now sunk into your flesh to their very bottom, while the labium, which formed merely the sheath for the whole, is bent up upon itself, ready again to assume its straight form, as soon as the disengaged lancets require its protection.

TONGUE OF BLOW-FLT.

The tongue of one of the common Flies (House-fly, Blow-fly, &c), is an exquisite microscopical object, from its extreme complexity and beauty. You are familiar with the way in which a fly, having alighted close to a drop of tea on the table, applies to it a proboscis with large dilated extremity, and presently licks it all up. You shall now see the curious implement by which this is effected.

The broad portion of the object before us, forming its bottom part, bristling with coarse black hair, is the front of the head of a Blow-fly. From the midst of this projects a dark brown mass terminating in two points, and inclosing a narrower and darker object with two long slender roots, dilated at their bases ; this is the pair of maxillce, altered and modified into a kind of sheath for the mandibles. On each side projects an elegant club, bristled with coarse black hair, and covered besides with a coat of very minute hairs; these clubs are the maxillary palpi.

But now we come to the terminal part, consisting of a pair of lobes, together forming a rounded triangle in their outline. This is the dilated and thickened termination of the labium, and is the instrument by which the liquids are so rapidly sucked up. It is impossible to describe this beautiful structure intelligibly ; and, indeed, it is not well understood even by those who have devoted their lives to this branch of natural science. The principal feature apparent is a wide clear membrane, through which runs with admirable symmetry a series of tubes. These tubes consist of four primary ones, all originating near the centre of the expansion, and radiating thence, two backward towards the two lateral angles of the triangle, and the other two nearly side by side towards its point. From each of these, along its outer side only, branch off the minor tubes, very numerous and close together, going off in a slightly sinuous line direct to the margin, diminishing regularly in their course, and at their extremities curving over, so as to bring their open tips to the surface of the skin.

The construction of these tubes is highly interesting : they are formed, like the air-pipes (trachece), of a multitude of horny rings ; but with this peculiarity, that the rings do not form a continuous spiral, but are separate and distinct, and are moreover imperfect ; for each wire (so to speak) does not perform a complete circle, but only about two-thirds of a circle, leaving a blank space ; and the tips of the wires end alternately in a fine acute point, and in a rounded fork, like the prongs of a pitch-fork. It has been said that these tubes are modified trachece; but this fact is by no means obvious to me; for, so far from their being connected with the general tracheal system, each of the four main tubes originates in an open centre, and each has an open extremity. I think it likely that they are so many suctorial pipes, through which the fluid to be drunk is drawn up, entering at their minute open tips, and discharging itself into the central cavity by the open basal extremities of the main tubes.

The most extraordinary modification of jaws, however, is the long spiral tube which is ordinarily coiled up under the face of a Butterfly or Moth, with which it sucks up the sweet nectar of flowers. Many flowers have a deep corolla, and most have the bases of their petals, where the nectar lies, so far from the level of the surface that probing is necessary to reach it. Bees can enter tubular flowers, and lick their bottoms; and even blossoms that are closed, as the Snapdragon, they know how to force and enter. But Butterflies, with their wide wings, in capable of being folded, cannot enter flowers bodily, and therefore a peculiar apparatus is given them for stealing their contents, as it were, at the doors.

Nothing is easier than to examine this beautiful organ with the naked eye; and much may be learned of its structure by means of a pocket lens. You may thus see in a moment that it forms a flat spiral of several coils, like the mainspring of a watch; that it runs off to a point, and that this point is double, for it is frequently seen separate a considerable way up. Hence you would probably infer that the organ consists of two equal and similar halves, united lengthwise. And so, indeed, it does; and these halves are the representatives of the maxillce or lower jaws of the Beetle, being thus greatly developed at the expense of almost all the other parts. The upper lip and the mandibles are discernible only in the form of three most minute plates ; the labial palpi are large and prominent, those well-haired points that project in front of the head, one on each side of the spiral. This spiral form of the maxillce is called antlia.

It is not, however, very easy to fix it in an extended condition on a slip of glass, so as that it shall lie flat throughout its whole length, without injuring the parts or so agglutinating them together that their structure is concealed or distorted, and in either case unfitted for microscopical examination. The specimen which I have prepared, from the mouth of the Small Garden White Butterfly, is stretched, and fixed in balsam, and will, I think, show you the structure under a high power very well.

Before we examine it, however, I will cite you the description of one of the most eminent of microscopical anatomists, Mr. Newport. He considers each maxilla to be composed of an immense number of short transverse muscular rings, which are convex externally and concave internally, the two connected organs forming a tube. Within each there are one or more large trachece connected with the trachece in the head. The inner or concave surface which forms the tube is lined with a very smooth membrane, and extends along the anterior margin throughout the whole length of the organ. At its commencement at the tip it occupies nearly the whole breadth of the organ, and is smaller than at its termination near the mouth, where the concavity or groove does not occupy more than about one-third of the breadth. In some species, the extremity of each maxilla is furnished along its anterior and lateral margin with a great number of minute papilla?. These, in Vanessa A talanta (the Bed Admiral Butterfly), for instance, form little barrel-shaped insects: their mouths. bodies, furnished at the free end with three or more marginal teeth, and a larger pointed body in the centre. There are seventy-four of these in each maxilla, or half the proboscis. Mr. Newport regards them as probably organs of taste. There are also some curious appendages arranged along the inner anterior margin of each maxilla, in the form of minute hooks, which, when the proboscis is extended, serve to unite the two halves together, by the point of the hooks in one half being inserted into little depressions between the teeth of the opposite side ; sometimes these are furnished with a tooth below their tips.

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