Chapter VIII.
Shells of Gairloch.
By the Rev. John M'Murtrie, M.A.
The following article appeared in Good Words in August 1883, and is generously contributed to this work by the author, the Rev. John M'Murtrie, lately minister of St Bernard's Church, Edinburgh, and now convener of the Foreign Mission Committee of the General Assembly of the Church of Scotland. Mr M'Murtrie has kindly added an appendix containing a list of shells, prepared by him expressly for this book. The article, which is inserted here with the consent of the Rev. Donald Macleod, D.D., editor of Good Words, is entitled—
"Spring-tide at Gairloch, West Ross—
A study of small shells.
"By the way, some people know as little about spring-tides as about small shells. I lately read, in a thrilling narrative of escape from drowning, 'It was neap-tide, and the sea was very far out.' Evidently the writer supposed that neap-tides are the very low tides, just as spring-tides are the very high ones. Of course, the truth is, that spring-tides both rise very high and fall very low; while neap-tides are the tides of least variation,—when, in short, the tides are nipped, and do not fall very low.[1] Once a fortnight there is a series of spring-tides, but, for reasons astronomical, some are much better than others. The half-hour of lowest recess of a first-rate spring-tide is precious to naturalists. You may chance to find them then at the edge of the sea, working, as if for dear life, under rock ledges and among seaweeds; and, wading as deep as they can, with bare arms they lift great stones from the bottom, and examine them for their living treasures. The sea in calm weather becomes very still during that half hour. When it is ended there occurs a remarkable thing, which I have never seen mentioned in books, but I think many shore-naturalists and bait-gatherers must know it. It is a sort of shudder of the sea, as though it awoke; there is a sudden strong susurrus,—the sound of that wonderful Latin word tells you its meaning,—the wash-sh of a swift little wave, breaking all along the shore and rising in every crevice at your feet, the first impact of a resistless power. At such a time I found myself at Gairloch, on the shore of Western Ross, beyond that gem of Scottish lakes, Loch Maree.
"Naturalists divide every shore into its upper, middle, and lower 'littoral zone.' I cannot write this paper without using a few hard words; littoral zone just means the beach between high and low tide-marks. Those plants and animals which live in the 'upper littoral' want no more of the sea than an occasional bath, or even merely its salt spray. The middle region is inhabited by species which prefer to be half their time under water, and the lower by those which agree with being usually submerged. Below the littoral we come upon the great laminarian zone, the region of waving laminaria, or sea-tangle. The best view of this submarine forest is from a boat, and you may have dipped an oar at low-water among its olive-brown fronds. These are not uncovered at ordinary tides, but a low spring-tide reveals them. Changed and weird is then the aspect of the sea, and the searcher has access to what he calls the 'upper laminarian.' It is but little harm after all that he ever does, if we take into account the prodigality with which the shore is furnished with life. But should a storm rage when the spring-tide is low, the waves tear up the tangles by hundreds, and pile them, with their countless freight of living shells and other creatures of God, in irretrievable ruin on the strand.
"At Gairloch I found that the rocky shore, while not precipitous, was yet so steep that the various zones and their subdivisions, which on a level beach may easily occupy a mile, were compressed into a very small space. Every few steps in a downward scramble brought one to a new vegetation and new forms of animal life. In particular, it was obvious that innumerable molluscs of the smaller, and therefore less-known species, found shelter and food among the seaweeds that densely clothed the rocks. These molluscs seemed brought to my hand that I might look at them. It occurred to me that no shell-gatherer, so far as I knew, had ever made it his study to know with exactness a compact little shore like this, to determine all the species of those myriads of living shells, to note their distribution and relative abundance, and to estimate the number of individuals.
"It was necessary first of all to devise a right method of investigation. To examine the whole shore was impossible and unnecessary. Plainly I must take samples. The rocks just below high-water mark were covered with a thick stubble of lichina, a small plant resembling the lichens of the land. Various species of minute sea-shells nestled plentifully at its roots. As much of the lichina as two hands could hold was soon scraped from the rocks, wrapped in paper, and called Parcel No. 1. Though months passed before I had leisure to scrutinize my prize, I may here state the result. When all the lichina and broken plates of barnacles and other débris had been removed, there remained twelve hundred and twenty perfect shells, which had been alive when captured; and when they were all put into a pill-box of the smallest size used by druggists, it was scarcely two-thirds full. The leading shell was a dwarf form of our smallest winkle, Littorina neritoïdes,—a species which may almost be said to dislike the sea, though it cannot live far from it. There were six hundred and three of this tiny winkle. Next came lasaea, a red and white bivalve (L. rubra), with four hundred and thirty-nine, mostly full grown. Small as it is, you may, with care and a good lens, open its valves and count a score of young ones within, each having a shell like that of its parent. Skenea (S. planorbis) was third, with a hundred and six shells, each like a short and not quite flat coil of brown rope. But a large skenea is less than the head of a small pin, and these were all young. The rest were a few specimens of the fry of all our other British winkles, and of the common mussel. Rissoa—so named from a naturalist of Nice, M. Risso—is a genus of humble spiral-shelled molluscs, which feed upon decaying seaweeds. Two specks in the parcel shewed themselves under the lens, by the bands which encircled their whorls, to be the young of Rissoa cingillus,—the rissoa, with the little belts around it.
"It would weary the ordinary reader to go through such details in the rest of this paper. I only seek to give him a glimpse into a world of life, of whose existence he was perhaps scarcely aware.