*

work for a fuller and more comprehensive account of this system, both anatomical and physiological, than I could find room for here. But, without entering into all the details, which belong to entomology generally rather than to our present subject, it will be necessary, to the full understanding of the natural history of wasps, to give more than a cursory sketch of these organs; the female, so important in a physiological point of view; the male supplying the most unfailing anatomical distinctions between different species.

It will facilitate our examination to bear in mind that there is a certain correspondence between the several organs in the two sexes respectively. Not that each organ has its exact counterpart in the other sex, but that the chief organs are evidently framed on a type common to them both. This community of type displays itself in the form and elementary structure of various parts whose functions may be very dissimilar. The clue fails us when we deal with parts which have no essential character by which we may discover them under another form. But where any such characters are present the morphological identity of these parts may be certainly proved. And the analysis, though it has been less studied, has no greater difficulties than, and is as full of interest to the anatomist as, that of the thorax.

The male organs of the wasp, as of other insects, consist of two symmetrical secreting glands, the testes, and an intromittent organ. It is in the * Entomology, translated,' pp. 181-223.

various forms which this last assumes that the specific distinctive characters are found. By this means the distinction between V. germanica and V. vulgaris, which the external markings of the two species often fail to give, has been established.* This organ consists of a horny case which occupies the end of the abdomen. It is formed of two valves opening along the middle line with a horizontal expanding movement very like that of the bivalve specula which Surgeons use for examining internal organs. The groove below is accommodated to the central spine, while the upper one receives the rectum. The form of the vent-cover is adapted to the sex of the insect. Instead of a scale being laid half-round the bowel, the bowel pierces the scale obliquely, and the same end is accomplished by, if possible, a still more simple mechanism than has been described in the female. The outer pair of valves end by a sharp, and more or less recurved point, which in Odynerus projects considerably beyond the end of the abdomen. Within, connected with the outer valves, lie a smaller pair of horny valves, which end, not in a hook, but in a filament which is clothed with fine hairs. These filaments lie parallel to each other and to the intromittent organ which is placed just beneath them. They re-appear in the caudal palpi of the female in a larger and more distinct form. The end of the intromittent organ comes fully into view on their removal. Spoon-shaped in V. vulgaris, bifid in V. germanica, the various forms which it assumes in different species are easy of recognition

* Smith's 'Catalogue of British Fossorial Hymenoptera,' &c. 1858. Plate V, Figs. 20 and 21.

with a common lens, and unfailing in their application. To the central spine which supports this we shall return, further on, in the female, where it appears in the modified form of the sting.

The testes are placed symmetrically, deep within the body. They correspond to the symmetrical ovaries of the female, not only in their general outline, but in the tubular arrangement of their internal structure. Like them, too, they run off into tracheal threads at the anterior extremity. Hunter* says that, while these glands are developed on both sides in the hornet, in the wasp usually only one is found. I have never examined these organs in a hornet; but in wasps I have generally found two glands, placed symmetrically, occasionally varying in size, and sometimes having tubular diverticula, or lateral pouches.

The male organs are obtained for dissection with very little trouble. The wasp, as fresh as possible, should be gently pressed on the abdomen, and, as the strong horny scales protrude, they may be withdrawn by the aid of the forceps, bringing with them the testes and the end of the alimentary canal. The appearance of the specimen is not in any way injured by the careful removal of the organs in this manner. For a more particular examination, however, they must be removed from the abdomen in the same way as, and, on account of the smaller size of the male, with even greater precautions than, the organs of the female, which come next under consideration. For their demonstration we need the water-trough, *Hunter. Posthumous Works On the Economy of Hornets and Wasps.' Vol. I, pp. 79 and 90.

and, if we can procure one, a dissecting microscope. We begin by removing the stomach with great care, dividing it where it dips down between the ovaries. The central air-trunk should then be cut through, as near the pedicle as possible, and gently drawn on, clearing away the trachea the while, till the egg tubes come into view. The whole mass may now be withdrawn, with a portion of the colon, in connection with the two last dorsal scales. We should procure as many of these ends of wasps as we can, and set them aside in glycerine. For the dissection is long, and we shall probably need a good many specimens before we succeed in fairly displaying all the parts.

other to a single mem

Now, placing one of these fragments in a watchglass full of water, steadied on an India-rubber ring, if we carefully remove the dorsal scales, and the sting with its bulb, we shall readily distinguish the two bundles of egg tubes. These converge at one end to an air trunk, at the branous canal; from which point we may most conveniently begin their description. This canal is called the uterus or oviduct, the latter name perhaps being the most correct, as it resembles in its functions the oviduct of birds rather than the uterus of Mammalia. Tracing this backwards from the point where it emerges from the muscular bulb of the sting, the first object which attracts notice is a little oval vesicle, distinguishable at once from the round, hard poison bag by its much smaller size and greater softness. It stands at right angles to a short tube, by which it communicates with the upper side of the oviduct. From its other end arise two small tubular glands. This is the spermatotheca, designed, as its

name implies, to contain the fertilizing fluid with which each egg is brought into contact as it passes

down the oviduct.

It

During this examination the eye may perhaps have been caught by a clear white glittering thread, connected rather with the root of the sting, as it might seem, than with the uterus. This is the gluten gland. It is the source of the glutinous secretion which coats the egg just before its final extrusion and, hardening into a skin like that which invests the eggs of snakes, fastens it to the cell wall. It is a clear transparent tube, distinguished from other gland tubes by not being marked by the presence of cells within it, and also by its much larger size. is found without difficulty, if the mass of sting and uterus be carefully torn up under the microscope; its bright opalescent appearance readily distinguishing it from the loose white shreds in which it lies entangled. But as it is very soft, it is liable to be separated from its connections. It is about a tenth of an inch or more in length, sometimes bifid at the free end; of irregular outline, about one eightieth of an inch in diameter at its widest part, but narrowing towards its orifice. It opens in the middle line, on the lower wall of the uterus, at the point where this joins the common vent or cloaca.

It should be observed that the dissection of all these parts is much more difficult in the wasp than in the honey-bee, where they are larger and firmer, and altogether much better developed. Indeed, the small wasps are far behind their larger sister, the hornet, in this particular. However, queen-wasps are much more common than queen-hornets, and