HOW WE FOUND THE MICROZOA. 293 



This idea was fiu-ther strengthened, as I had previously observed 

 these shells were iilled, not with the red clay in which they were found 

 imbedded, but with a greyish- white sandy material — not occurring else- 

 where 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 Tunitellse 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 spiculse, and the spines of Echini. So 

 thus was accomphshed, after many unsuccessful attempts, the discovery 

 of the Microzoa in the boulder claj^s. 



The next question was, whether this was a mere local phenomenon, 

 or was general in the boulder clays of the district. In order to deter- 

 mine this, in the spring of the following year, 187-5, I made various 

 excursions, and I found the Microzoa in the Gastropoda of the boulder 

 clay of Madeley, in Staffordshire ; Wliitchiu'ch (Salop,) Colwj-n Bay 

 (Denbighshire,) St. Asaph, Hawarden in Fhntshire, Dawpool, Newton, 

 (Cheshu-e,) also 700 feet above the sea at Macclesfield and Arnfield, 

 (Cheshire,) Liverpool and other parts of Lancashire, the Isle of Man, etc. ; 

 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 ourselves how these Gastx'opoda became 

 filled with the grejish-white sand, though they occurred imbedded in a 

 matrix of red boulder clay? In the early part of 1875 there was a short, 

 but, for the time, a veiy severe fi'ost. At the mouth 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 Cheshii-e shore. This space is 

 covered with water at half tide. The dead shells of the MoUusca, 

 Ostracoda, and Foi'aminifera, which hve 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 he 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 '^^th 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 Gastropoda, filled with silt and bi'oken shells, these tiny ice-rafts 

 floated short distances away, distributing, as they melted, then- 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, Ii-eland. My mother, Mrs. Shone, on examining this debris, 

 observed that the fiy 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 them and repeat the phenomena of 

 the Gastropoda of the boulder clays. 



