Stuart Bailey, age 72, of Victoria, B.C., Canada, for his question:

Are guinea pigs really pigs?

The trademark of the farmyard pig is a curly tail    and there is a tale about the tail of the guinea pig. If you lift the furry little eutie by his tail, his eyes will fall out    or so they say. But this cannot be proved, for the guinea pig has no tail at all. Scientists, however, pay no attention to tails or tales when classifying the various animals.

All the known animals arc classified in large groups called phyla, which is the plural of phylum. Pigs and guinea pigs belong with all the backboned animals in the Phylum Chordata. The backboned vertebrates arc subdivided into some 10 classes. Pigs and guinea pigs belong in the Class Mammalia. They arc both warm blooded, air breathing animals who give birth to live youngsters and feed their infants on mother's milk.

Giant whales and tiny mice, fluffy cats and crusty armadillos arc also mammals, hence the class Mammalia is subdivided into some 20 different orders. The differences between the pig and the guinea pig arc so marked that they arc placed in different orders. Mr. Porker belongs in the Order Axtiodactyla,, meaning even toes. The cute guinea pig belongs in the Order Rodentia, meaning the gnawing animals.

The pig has a pair of toes which forms a cloven hoof on each foot. He is not choosey about his diet, and his sturdy teeth can cope with any meat or vegetable that comes his way. The guinea pig's soft toes end in hard nails. Each front foot is four toed, each hind foot is three toed. He is a strict vegetarian, and his gnawing teeth can cope only with a diet of mealy mash and soft plant food.

Orders are subdivided into families. The family of the farmyard pig is Suidae, from the Latin word for hog. The guinea pig belongs in the Family Caviidae, which is named for the South American Cavy. Mr. Guinea Pig's wild ancestors were natives of the Andes, and long ago the Incas domesticated them for food.

In the 1500s, some of these tame ancestors were sent to Europe, where they were named guinea pigs. The furry travelers grunted like hungry pig_lets. They arrived on Guinea Traders, ships that carried goods from the Guinea Coast, and the little charmers never reported the fact that Guinea was just a port of call on their long journey from the new World to the Old World.

Wild cavies still live among the lofty Andes. They are drab fellows with coats of short grayish or brownish fur. The Incas developed tame varieties with silken coats of rusty red, brown and white. Now We have end1ess varieties, including some with long fur and some with coats of pinto patches. Guinea pigs make clean and gentle pets. Many of them are helpers  of medical science, used as laboratory animals in the endless fight against disease.