Their decline had started by the end of the Silurian period and they were extinct in another hundred million years. The reason for their decline is unknown, but perhaps it was related to some decided change in temperature and distribution of the waters. Remarkably well preserved remains of the monsters have been found imbedded in limestone on Oesel Island, in the Baltic. During the Silurian era life was just starting to emigrate from the oceans and establish a precarious foothold on land. Among the earliest land fossils are those of small scorpions, distantly related to the erstwhile master race. The euripterids themselves, however, never tried to leave the sea. _Worms With a Thousand Eyes_ There are worms with a thousand eyes. They are, for the most part, animals of the dank, dark floors of tropical rain forests. They are narrow, brilliantly colored ribbons of slimy skin which glide at a speed of about six feet an hour over damp moss and leaves in the everlasting twilight. When alarmed they can break up instantly into scores of “blobs of slime” and in a few hours each piece will become a complete new worm. One of them can eat five-sixths of its own body and entirely recover. These fantastic creatures are the terricola or land planarians—lowliest of worms and one of the lowliest forms of animal life. Only the microscopic protozoa, the slime moulds, the sponges, jellyfish, and corals are more primitive. They range from fractions of an inch to nearly a foot in length. They are hunters and scavengers. Nearly all are creatures of darkness and dim light—survivors of the haunted dawn of life on earth. They probably are quite close to the ancestral form of all worms. All are free-living animals, although related closely to the degenerate flukes and cestodes, which are internal parasites of man and other animals. They belong to an enormous clan. There are several hundred known species and perhaps as many more still unknown. These worms are found over most of the world but most abundantly in the damp tropical and sub-tropical rain forests. They are seldom seen in nature although they are fairly well-known in experimental biology classes, for which they are purchased from dealers. Australia has about sixty species. America may have many more, most of which remain undescribed. One would be likely to come upon them only by accident. Among these land planarians are some of the most fantastic creatures of the animal kingdom. They have been described as “gliding strips of skin.” The family includes some of the most brilliantly colored of all living things. They probably represent the earliest traces of eyes and brains in the world.