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Updated: June 21, 2025
The evidence suggests that both the free-moving and the stalked Echinoderms descend from a common stalked Archaean ancestor. Some primitive animal abandoned the worm-like habit, and attached itself, like a polyp, to the floor. Like all such sessile animals, it developed a wreath of arms round the open mouth.
At the close of the first Great Time called Archaean the continent south of the region of the great lakes, excepting a few islands, was still submerged beneath a shallow sea, and therefore no portion of the Mississippi was yet in existence.
Nor does it cease till the progress of the warmer day removes the northern ice-dam, sets free the flood, and the region of archaean rocks stands bare and dry.
Their story evidently goes back, for millions of years, deep into those mists of the Archaean age which we were unable to penetrate. We turn therefore to the zoologist to learn what he can tell us of the origin and family-relations of these Cambrian animals, and will afterwards see how they are climbing to higher levels under the eye of the geologist.
Then, for some reason or other, there was a rest for a while a few hundreds or thousands of years and the masses of sediments became cemented into sandstone and shale, which we call the Cambrian formation, or the Tonto sandstone. This is to be seen resting both upon the Archaean and Algonkian from the porches of El Tovar.
The Medusa really descends from one of the plant-like animals of the early Archaean period, but it has abandoned the ancestral stalk, turned upside down, and developed muscular swimming organs. Its past is betrayed in its embryonic development. As a rule the germ develops into a stalked polyp, out of which the free-swimming Medusa is formed.
Planed and smoothed off as they are, the Algonkian and Archaean masses are to be submerged once more in the ever receptive ocean. A period of subsidence occurs, and the whole area is soon hidden under the face of the sea. But, all around these are masses, some day to be mountain peaks, that refuse to sink again into the sea. Then the forces of the air assail them.
Apparently this stage is reached at the end of the Archaean, and a great rise of the land probably protracted during hundreds of thousands of years takes place. The shore-bottoms round the primitive continent are raised above the water, their rocks crumpling like plates of lead under the overpowering pressure.
That section of geology is still in its infancy, it is true. A day may come when science will decipher a long and instructive narrative in the masses of quartz and gneiss, and the layers of various kinds, which it calls the Archaean rocks.
But in most places this rock lies deep under the waters of the oceans, or buried below the heaped up strata of the formations which the hand of time piled thickly upon it. Only here and there can it still be seen as surface rock or as rock that lies but a little distance below the soil. In Canada, more than anywhere else in the world, is this Archaean formation seen.
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