Garden Ponds are a great way to enjoy your California backyard

Snails, Shrimps And Aquarettes SNAILS, SHRIMPS AND AQUARETTES

Besides plants and fishes the pond should house a variety of other creatures, not so much because they are beautiful or interesting, but because they will benefit her ladyship the plant and his lordship the fish.

The molluscs, in which phylum of the animal kingdom are included the cockle, oyster, limpet, etc., provide the scavengers. The freshwater snail is perhaps the best known member of this fraternity and it is one of the most useful. It lays a great quantity of eggs, usually on the underside of lily leaves, and fishes eat these with relish. The greatest value of this animal, however, comes from its ' gleaning ' habits. The teeth are rasp-like and are set in a flexible ribbon which the creature can extrude or retract at will. This ribbon, or tongue, is worked back- wards and forwards as the snail pursues its way, and the thin clean line so made is quite noticeable.

The Ramshorn Snail is the most common species sold in England ; it is a flat, convoluted animal, dark brown in colour with occasional darker bands. The shell itself has a number of small ridges across it. Several other species are obtainable, one in particular is quite handsome, being a deep red colour. In the pool, of course, where the snails are rarely seen, the common variety suffices.

The Fresh-water Winkle (Paludina vivipara) is a really pretty little chap ; the shell has a fragile, semi-transparent look and the colour is fawn with grey stripes. The shape is pyramidal. The young are born alive in the Summer and are recognisable as snails from the onset. Fortunately, this snail never grows to any size, for, although an efficient scavenger, it is rather impatient and sets about the plants before they have died.

The Limnae or Ear Snails are scavengers also, but, from their greater size and slight partiality for growing vegetation, should be reserved for large ponds and lakes. In fact, the Great Pond Snail (L. stagnalis) should be introduced into all large stretches of water ; it will keep the rapidly spreading plants under control. Six species of Limnae inhabit the streams and ponds of the countryside and all have ear-shaped mouths. L. auricularia is the most interesting species for the aquarium ; it is as though made of horn and the mouth is particularly large.

Physa, a closely related genus, has smaller individuals and the shell is highly polished ; moreover, the convolutions are left-handed.