Different species of sea-weed are frequently covered by minute shells—weeds should always be carefully examined. Many of the smaller and microscopic shells are found at high-water mark among the fine dross and drifted fragments of shells; this sand should be brought home and examined at leisure. To facilitate the process a small wire-cloth sieve should be made of about six or seven inches square and all the sand sifted through it and the shells left.
Molluscous Animals. Many species of worms and other soft, invertebrate animals are to be caught also by the dredge. There is no way of preserving these animals except by putting them in spirits. Animals of this kind are still very imperfectly known, notwithstanding the researches of Lamarck, Poli, and other celebrated naturalists. Every opportunity should, therefore, be embraced of bringing them home; indeed, we are still little acquainted with those which inhabit our own seas.
When animals of this kind are procured in foreign parts a careful noting of the latitude should be taken; and it should be stated whether they live singly or are congregated, if they are phosphorescent, and if they were taken in deep water. And as these animals are very liable to lose their colors by being put in spirits, a careful noting of these should be taken whenever they are caught, as the colors are very evanescent; or, what would be still better, a drawing of the animal should be made.
Intestinal Worms. Whenever we have killed either a quadruped, bird, or fish, we should carefully examine the stomach and intestinal canal of the animal to see if there are any worms; indeed, there are few animals without them; they must also be preserved in spirits. Besides the stomach and intestines, worms are also found in the livers and other parts of the body; also in the back of Skates and various fishes.
INSECTS.
This class is subject to infinite variety, according to climate and soil. The entomologist, or the mere collector, must not confine himself to those whose beauty of coloring renders them attractive, but collect all that come in the way. Those species which have wings, and fly around plants, we take by means of gauze nets, and also those which swim in the water. Those which live on putrid substances, and such as are disagreeable to the touch, are seized with pincers; they are first put into camphorated spirits to render them clean. Trees are the habitations of innumerable insects; many of them skulk under the old rotten bark, and others attach themselves to the foliage. A cloth should be spread under the trees, or an umbrella, and the branches shaken with considerable force, when they will fall down, and may then be caught.
Insects are killed by making a crow-quill into a long point and dipping it into prussic acid; an incision with it may be made immediately below the head of the insect betwixt the shoulders, which usually produces instant death. But this acid must be used with much caution, because its effects are almost as instantaneous and fatal in the human subject as in the lower animals. When cork cannot be had for lining the bottoms of the boxes, a layer of beeswax may be used in its stead. The pin should be deeply sunk in this substance, as it is more liable to loosen than when in cork.
It is of much importance to procure the caterpillar as well as the insect, and, in this case, some of the leaves on which it feeds should be placed in a box beside it, so that it may reach maturity. A small perforation should be made in the box for the admission of air.
Every kind of insect, except butterflies, sphinges, and moths, may be preserved in bottles of spirits, which will not injure them; when they are taken out they are immediately placed in the position in which it is wished to preserve them, and they are then allowed to dry. Another mode of preserving coleopterous insects, such as beetles, etc., is to put them in a dry box amongst fine sand. A row of insects is placed in a layer of sand, and then a new layer of about an inch in depth laid on the top, and so on till the box is filled. This mode of packing will not, however, do with soft insects and those having fine wings.
It is extremely desirable that all the different kinds of Spiders should be caught, particularly those said to be venomous; also termites, or white ants, the different scolopendra, and gaily worms, etc. The nests of spiders and other insects should also be sent home; in short, every insect which is remarkable, in any way, either for its history or properties.