SCIENCE SIFTINGS

New Zealand Tablet, 25 August 1921, Page 46

SCIENCE SIFTINGS

I— ~ = By “VOLT” ~

Eyes that Make a Journey : The Wonderful Story of the Toothsome Plaice.

Every spring sees immense activity amongst the vast numbers of plaice which inhabit the waters of the North Sea. /

The females are searching for suitable places in which to lay the countless millions of tiny eggs upon the fate of which depends an important part of our food supply. The plaice is second only to the herring as a food fish. Every year the inhabitants of this country eat no fewer than 150,000,000 of these fish (says Tit-Bits). The plaice eaten in these islands alone in a single year would form a solid mass of fish as big as the Houses of Parliament.

A few are caught off the South Coast, but the vast majority come from the North Sea. Think for a moment of the task Nature has to perform in order to provide these enormous quantities of plaice for our use. Remember, too, that besides ourselves the French, Belgians, Dutch, Germans, Danes, Norwegians, and Swedes are all taking their toll. If the plaice were not a most prolific fish, he would soon be wiped out of existence.-

Every female lays from 150,000 to 200,000 eggs. They are deposited in the shallow waters round the coast, and directly they are laid attacks upon them begin. There is no delicacy beloved by sea creatures so much as the eggs of a fish. Put a piece of any kind of hard which is a solid mass of eggs—into an aquarium, and you will soon see the truth of this remark. Enormous numbers of the eggs are devoured before they can hatch. But they are so numerous that plenty survive, in spite of all attacks. From each egg a curious little creature makes its appearance in the course of a week or two. It is so tiny that a hundred could rest easily upon the surface of . a shilling. It is perfectly transparent, except for two wee black specks—its eyes. At first it moves very feebly; as it has not strength enough to forage for food, it is provided with a little bag of nourishment attached to the under side. The contents of this bag are absorbed during the first few days of its life, at the end of which time it is able to fend for itself. The youngster grows very rapidly, and each day sees him getting broader and broader. At length there comes a time when he can no longer keep on an even keel; he loses his balance, and topples over on to his side. And it is always the same side—the left. Now begins a curious transformation. The little plaice's upper side becomes colored; the skin takes on a dark brown tint, with a mottling 0 f brilliant red and orange spots, in order to harmonise with the sand upon which the fish rests. But, strangest process of all, the left eye begins to move round the head. Gradually it climbs towards the top of the head; it moves slowly across the forehead, and finally comes to rest close to the right eye Once he has become a real flat fish the plaice grows more slowly. At a year old he is about two and a-half inches long. The plaice we usually see on the fishmonger's slab is a five-year-old.

We can tell the age of a plaice exactly. In his ear is a hard bone called an ear-stone, which forms a lightcolored ring for each summer its owner lives, and a dark one for each winter. By counting these rings we can'find the plaice's age just as easily as we discover a horse's a K © from his teeth.