Insects supply us with another series of beautiful objects, viz., the _feet_.[D] These are sometimes simply dried and mounted without any medium, as before mentioned; but most of them are rendered much more fit for examination by using balsam in their preservation, as it greatly increases their transparency. The smaller kinds may be dried with gentle pressure betwixt blotting-paper, and then immersed for some days in turpentine, without requiring the treatment with liquor potassæ. This immersion will render them beautifully transparent, when they may be mounted in balsam in the usual manner. [D] See Mr. Hepworth’s interesting articles on the fly’s foot in the second and third volumes of the _Microscopic Journal_. It is, however, sometimes found difficult to fix the feet when _expanded_, in which state the interest of the object is greatly increased. Mr. Ralph recommends the following mode:--“First wash the feet, while the insect is yet alive, with spirits of wine; then holding it by a pair of forceps close to the edge of a clean piece of glass, the insect will lay hold of the upper surface by its foot, then suddenly drop another small piece of glass over it, so as to retain the foot expanded, and cut it off with a pair of scissors, tie up and soak to get rid of air.” Mr. Hepworth says that he never found any difficulty in expanding the foot on a drop of water or well-wetted slide, and laying a thin glass cover over it, tying with thread, drying, and immersing in turpentine. The mouth, also, with its organs, is an interesting object in many insects. That of the common fly is often made use of, and is comparatively easy to prepare. By pressing the head, the tongue (as it is commonly termed) will be forced to protrude, when it must be secured by the same means as the foot, and may be subjected to the soaking in turpentine, and mounted as usual. The honey-bee is, however, very different in formation, and is well worth another slide; indeed, even in insects of the same class, the differences are many and interesting. Another worthy object of study is the _respiration_ of insects, which is effected by tracheæ or hollow tubes, which generally run through the body in one or more large trunks, branching out on every side. These terminate at the surface in openings, which are termed _spiracles_, or breathing organs. The _tracheæ_ often present the appearance of tubes constructed by a twisted thread, somewhat resembling the spiral fibres of some plants. These are very beautiful objects, and are generally mounted in balsam, for which reason they are mentioned here; but as they evidently belong to the “dissecting portion,” they will be fully treated of in another place.