Most of the Scottish lochs* have their monsters. A large group of Gaelic stories tell of the manster of the deep which came into a loch, causing a high tide; it claimed a human sacrifice and when lots were drawn the king’s daughter was the victim. The young and beautiful princess had to go to a selected spot and await the coming of the monster so that the whole realm might not be ravaged.

The king’s daughter was accompanied by warriors to a green mound by the sea-side, but these armed men fled af the first hint of peril. A brave young man who had been acting as herd came to defend the princess and lay down to sleep until the monster appeared. To awaken him from his “magic sleep’’, during which he acquired “power’’, the princess had to cut off a portion of his ar or a joint of his little finger or a portion of his scalp.

As the young hero slept, the princess saw the three-headed monster approaching in a squall of wind, while the tide rose and the loch grew stormy. She awoke the young man by slightly mutilating him as instructed and on the first day he cut off one of the monster’s heads. The combat was repeated on the second day, when another head was cut off. On the third day the hero cut off the last head and the monster was slain. A monster is reputed to haunt Loch Morar, Lochaber, the deepest loch in Scotland. It is known as “Morag’’ and has been described as “a huge, shapeless, dark mass, rising out of the water like an island.’’

And what about the Loch Ness Monster (Nessie)? Is it a rotting tree trunk, a killer whale that has penetrated the loch from the sea, a plesiosaurus from an age 60 million years ago, a giant eel, or a floating mat of vegetation?

There have been at least two deliberate hoaxes: an imprint on the lake shore made by a hippo’s foot mounted on an ash tray and a whale’s jaw lifted from a rock garden* in York. Serious investigations there have been in plenty, and in June 1963 the Loch Ness Investigation Bureau was set up with ten observation stations. There were 40 recorded sightings that month. The Highlands Development Board even donated £1,000 to the Bureau. There have been anchored balloons taking time-lapse photos,* and underwater sound recordings.

Early one morning in 1934 a young woman looked out of the dining-room window of the house where she worked as a maid and saw about 300 yards away in the waters of Loch Ness the “largest animal I have ever seen’’. She borrowed her employer’s binoculars and watched it for 25 minutes. It had, she said later, a “giraffe-like neck, and an absurdly small head out of all proportion to the great dark-grey body,’’ which was the colour of an elephant. As it twisted andturned its back arched into two or more humps. Then it lowered its head into the water and swam away.

That was the year in which the first book about the socalled Loch Ness Monster was published.

Peter Costello in his book “In Search of Lake Monsters’’ examines the many theories about these creatures, not omitting aspects legendary, supernatural, hystorical and autosuggestive. His own conclusion, after dismissing all the other explanations, is that the“monster’’ is a warm-blooded mammal with a fur coat more specialised for a purely aquatic existence than any known seal. Hesays the scientific name proposed for the animal (translated from the Latin) is “the big sea-lion with a long neck’’.

Nothing is known about their reproduction, birth, growth or maturity. Yet there cannot be just one of the Loch Ness animals. To maintain a population of them in the lake, he contends, there must be at least 15 or 20.