stocked by special acts of creation; curiously enough, when a boy, I believe before reading any books, I was much puzzled at seeing some living thing in a newlyformed pool, and remember concluding that it must have been created there! Mr. Clement Reid, who has attended to this subject, has been in the habit of noting from time to time the species occurring in artificial ponds and other isolated waters; by so doing, as he puts it, one can see the accumulated results of many years' dispersal, and can get some idea as to the extent to which it must be going on." As a rule, he tells me, such waters only contain Limnææ (generally L. peregra), but the species auricularia, truncatula, stagnalis, and palustris also occur, associated, sometimes, with the smaller Planorbes (generally spirorbis and vortex), and Physa fontinalis. The presence of bivalves, he adds, "is quite exceptional; the smaller Pisidia, especially P. pusillum, occasionally occur, and I have once found Sphærium corneum, but never Unio or Anodon;" operculate pond-snails are almost invariably absent. More recently, this observer has published an able paper on the "Natural History of Isolated Ponds," based, for the most part, upon observations made on the South Downs.1 These undulating chalk hills, it is stated, constitute a pre-eminently dry district in which, in order to provide water for the cattle, ponds have to be dug at comparatively short distances from each other. When rendered impervious by puddling with clay or chalk

1 Clement Reid, Trans. Norfolk and Norwich Nat. Soc., v. (1892), 272.

mud, or sometimes by a lining of concrete, such “dewponds" retain a store of water, except during droughts of exceptional duration, derived from "the rain, dew, and condensation of the mists which often hang on the tops of the hills." Many occur at the distance of a mile or even two or three miles from the nearest stream or marsh, and, as the Downs rise to 800 feet, their average height is fully 200 feet above other water, so that the aquatic animals and plants found therein must certainly have been "transported uphill as well as across uncongenial tracts of dry grass," or be descended from ancestors thus transported. Notwithstanding this extreme isolation, however, the ponds are often found to be inhabited by fresh-water shells. Two, at least, of the three examples given by Mr. Reid were thus inhabited: (1.) Large dew-pond on the open Down nearly a mile east-south-east of Amberley Station; height, 310 feet above the sea, and 300 feet above the marshes of the Arun; nearest water, the marshes of the Arun, distant half a mile. Noted 15th November, 1884. This pond has evidently been made several years, and is now full of water-plants. The species observed, were Juncus (not in flower or fruit, though very abundant), Potamogeton densus (very common), Ranunculus aquatilis, Chara, and a single small, but vigorous tuft of Elodea canadensis. (I have apparently omitted to note the mollusca from this pond, if there were any).

(2). "Redlion Pond, on the open Down, three miles south-east of Lewes ; height 540 feet above the sea, and 530 feet above the marshes of the Ouse; nearest water,

the marshes of the Ouse, distant seven furlongs. Noted June, 1890. The species observed were Limnæa peregra, Ranunculus aquatilis, and Elodea.

(3). "Small pond by the side of the high road, half a mile west of Christ Church, Stansted (near the Hampshire border); height, 312 feet above the sea, and 220 feet above the nearest stream; nearest water a small stream, distant about two miles to the south-south-west, but apparently containing neither of the plants found in the pond. Noted September 25th, 1891. The species found were Limnæa peregra, Planorbis spirorbis, Potamogeton natans, Zannichellia palustris, all abundant; the two plants in fruit, and carrying many eggs of Limnæa. Zannichellia occurs again in a pond in a brick-field, two miles to the south-west, but does not fruit there; the nearest natural station for it seems to be in the slightly brackish marshes near Emsworth, four miles to the south. Potamogeton natans can probably be found within three miles. This pond is overshadowed by a large oak, and supplied by dew and rain off the road; neither of the plants, however, is a species likely to be brought to the locality by carts or on the hoofs of horses."

The absence of bivalves from such ponds, it is true, need hardly be regarded as surprising, but I am unable to agree with Mr. Reid in thinking that the occurrence of the smaller kinds in isolated waters is likely to be altogether exceptional. The creatures may easily be overlooked, and Mr. Reid tells us, in the paper just quoted, that he "could only stay to note the common and conspicuous animals and plants." The catch-water

or dew-ponds of the Lincolnshire Wolds, dug out of the chalk and puddled with clay, though often or usually dry in summer, do not essentially differ, I imagine, from those of the Downs. Recently my brother showed me a pond of this kind, the most isolated he could find about Louth, situate on one of the highest of the rolling chalk hills in the neighbourhood, at a great distance from any other water, and in this were bivalves of two kinds, Sphærium lacustre and Pisidium pusillum, the former in good numbers. In ponds on lower ground and less remote from other water (but perfectly isolated and out of the reach of floods), where the conditions of existence are probably more congenial, small bivalves certainly seem to occur with some frequency. Uncongenial conditions, Mr. Reid remarks, have probably much to do with the poverty of the fauna and flora in dew-ponds. Mr. Musson, who, also, has paid some attention to the subject, speaks of Sphærium lacustre as a species commonly found in "upland ponds" [ponds without inlet or outlet, dependent directly on rain-water for their supply, as distinguished from such as are affected by floods and rivers], in which also, as he adds, Sphærium corneum, more generally found in rivers, canals, &c., occurs occasionally. A small "upland" horse-pond, near the Hemlock Stone, near Nottingham, examined by him during 1883 and 1884, was inhabited by six kinds of molluscs, of which three were bivalves: Sphærium lacustre and two species of Pisidium; and three univalves: Planorbis nitidus, Pl. nautileus, and Ancylus lacustris-a strange set of species, as he remarks,

to have come together in one small pond. I will here add particulars of the Lincolnshire catch-water pond referred to, and of one or two other isolated ponds, &c. Details, in such cases, must always be tedious, but the subject, as it seems to me, is an interesting one.

Pond at Welton-le-Wold, Lincolnshire.-A small pond, about nine yards in length, on the Wolds not far from Louth, near the crown of Bunker's Hill. A great distance from any other water, and far above the nearest stream. Between arable fields, but with no ditches near. Probably old, having existed, perhaps when the wold was unenclosed; remains of a rough pump are to be seen on one of the banks. Water derived solely from rain, &c., falling in the immediate neighbourhood. No water-weeds are likely to have been planted by man. Four species of shells occur: Sphærium lacustre, Pisidium pusillum, Limnæa peregra, and Limnæa truncatula.

Pond at Riplingham, Yorkshire.—Mr. F. W. Fierke, of Hull, has favoured me with particulars of a somewhat similar pond on the Yorkshire Wolds, at Riplingham, scooped out of the chalk and laid over with clay, and supplied with water by rain and surface drainage only. The ever present Limnoa peregra, among higher organisms seemingly the only inhabitant, exists in countless numbers, almost covering the bottom. There are no water-weeds. Many ponds of this kind,

1 Specimens were exhibited at the Conchological Society on 7th October, 1891; see "Journ. of Conch.," vi. (1891), 398.