Notes on Collecting and Preserving Natural-History Objects

by Unknown

From causes which need not be explained here, the shells living in some ponds are all much eroded, or coated with a ferruginous deposit; it will be desirable therefore to find out the localities where specimens are in the best condition, so that you may have typical specimens for comparison before an extensive collection is made.

Our experience is, that though a considerable number of species may be obtained from a ditch or pond, yet a few are found as the sole molluscan tenants of particular sheets of water; that lakes exhibit a dearth of life, and that the greatest variety is often to be met with in canals; but should a search be carried on in them, avoid the towpath side, for reasons that a little thought will readily suggest.

Living near the sea, and within a short distance of wooded hill-sides, we had within a limited area such a variety of physical features that we were led to infer the existence of a rich molluscan fauna for the neighbourhood. Our second excursion was devoted to a search for snails along the sea margin and shores of the estuary. Proceeding along the low sand-dunes—at first sight a most uninteresting spot—Helix caperata, H. virgata, Bulimus acutus, and a few other snails, were found clustering upon the low stunted vegetation in such numbers, that handfuls might have been gathered within an area of a few square feet. Leaving the seashore, our way led us over the foreshore of the mouth of the river, crushing under our feet at every step shells of Cardium edule, Scrobicularia piperata, and a few other bivalves which find a congenial habitat in such situations. Gaining the muddy margins of the higher part of the estuary, Conovulus was looked for, and found under the stones along the high-water mark. Higher up the river the rejectamentum on its banks was carefully turned over, and we were successful in securing a number of land shells. The animals, of course, do not live in such places; but their empty shells, which alone were found, had been brought down from the land surface by the agency of the streams and tributaries of the river. Nevertheless such an omnium gatherum should demand attention, as its contents give an insight into the character of the land and freshwater forms within the area of drainage of the river.

The number of estuarine species which have a place in our works devoted to British land and freshwater snails is very few, and the majority, moreover, are confined to the margins of the tidal rivers in the south of England. Thus Assiminea Grayana, Hydrobia ventrosa, and H. similis, live on the mud banks beneath the shade of sedges and rushes, skirting the Thames below Greenwich. To gather these small shells singly is a tedious operation; but if a thin piece of flat wood, or other substitute as the ingenuity of the collector suggests, be used to scrape lightly over the surface of mud, transferring the mass to the dredger, and washing in water, a number of specimens sufficient to stock every private cabinet in the country may be obtained in a short space of time.

For the third initiatory excursion our steps were directed inland, and as we proceeded the hedgerows, mossy banks, and margins of watercourses were diligently searched, finding a Helix here, a Pupa or a Succinea there. Gaining the woods, we turn over the damp leaves, grub under the clumps of ferns and wood-rushes for small Helices, Pupæ, and the like; scan the trunks of the trees for the climbing Clausiliæ, Bulimi, and Helices, not unmindful that each little dirt-like mass is probably a Bulimus obscurus, which, by covering its shell with mud, thus exhibits a protective faculty, and often escapes detection. Raise the rotting bark for Balia; lift the stones at our feet, or roll away a log for Helicella, and other small shells which usually live in such situations.

From all this we learn that each species affects certain stations, and therefore, with the knowledge of the circumstances in which they are found, we may set out with some definite idea as to what we are likely to meet with; and, in consequence, when to collect and where to collect are regulated by the unvarying habits of the objects of our search.

Now, a large portion of the life of most land snails is passed in a state of sleep. Those living in open situations are inactive during the heat of a summer's day, and when there is continued drought; but on the first shower, or after the fall of dew at night, they recover and move about in search of food. Cold acts much in the same way as heat, and with the fall of the leaf they retire to winter quarters in crannies of rocks, crevices of walls, under heaps of decaying vegetation, &c., or bury themselves in the soil, there to hybernate till the genial showers of spring awaken them.

The best time of the year for collecting is in the autumn, when the shells are full-grown. Those collected in spring have lost much of their original beauty by exposure to the rains and cold of the winter months.

As regards the particular time of day to collect with advantage, it has already been implied that a search in an open country should be prosecuted after a shower of rain, or during early morn. In damp woods, where throughout the day the air is sufficiently moist to maintain the animals in full activity, no such considerations determine the best time for collecting. In such places, light is usually the desideratum, and consequently I have found that a search conducted at midday in a clear sky has been amply rewarded.