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This idea was further strengthened, as I bad previously observed these shells were tilled, not with the red clay in which they were found imbedded, but with a greyish-white sandy material- not occurring elsewhere in the boulder clays. So I put the idea that evening into practice by washing out, in a test tube, the substance which filled the inner whorls of the Turritellæ and other Gastropoda, After pouring off the fine muddy particles, there remained behind a fine sandy residuum which, on being placed beneath the microscope, I found to be full of Foraminifera, Ostracoda, Sponge spiculæ, and the spines of Echini. So thus was accomplished, after many unsuccessful attempts, the discovery of the Microzoa in the boulder clays.
The next question was, whether this was a mere local phenomenon, or was general in the boulder clays of the district. In order to determine this, in the spring of the following year, 1875, I made various excursions, and I found the Micrazoa in the Gastropoda of the boulder clay of Madeley, in Staffordshire; Whitchurch (Salop,) Colwyn Bay (Denbighshire,) St, Asaph, Hawarden in Flintshire, Dawpool, Newton, (Cheshire) also 700 feet above the sea at Macclesfield and Arnfield, (Cheshire,} Liverpool and other parts of Lancashire, the Isle of Man, &c.; in fact, wherever on the west coast I found Gastropoda in the boulder clay, the Microzoa abounded in the sand within them.
We then began to question our selves haw these Gastropoda became filled with the greyish-white sand, though they occurred imbedded in a matrix of red boulder clay? In the early pert of 1875 there was a short, but, for the time, a very severe frost. At the month of the Dee there is an island, called Hilbre, some five acres in extent; it is distant about a mile and a half across the sands from the Cheshire shore, This space is covered with water at half tide. The dead shells of the Mollusca, Ostracoda, and Foraminifera, which live in the laminarian zone, are cast up and left by the receding tide between the ripple marks. The dead shells of the Gastropoda, as they lie in these hollows, get more or less filled with the greyish-white silt containing the Microzoa, The frost was severe enough to freeze the sea-water left by the tide in these hollows. Consequently the Gastropoda filled with this silt, the broken shells, &c., were enclosed in thin sheets of ice, which were broken up on the return of the tide, and such as were cast ashore on Hilbre Island were piled together and frozen into blocks. When the thaw commenced, it set the blocks free. Charged with the Gastropada, filled with silt and broken shells, these tiny ice-rafts floated short distances away, distributing, as they melted, their load of broken shells, and casting the silt-filled Gastropoda over the mud flats of the delta of the Dee.
Recently Mr. R. D. Darbishire, B.A., F.G.S., gave me some silt containing Foraminifera, &c., gathered from the beach at Gorteen, Connemara, Ireland. My mother, Mrs. Shone, an examining this debris, observed that the fry of the Gastropoda, which abounded in it, were filled with this Foraminiferal silt, and only awaited the formation of ground ice on the shore, to transport then and repeat the phenomena of the Gastropoda of the boulder clays.