[Illustration: COMPANIONS AND FRIENDS.] The last nine lessons have been occupied with brief descriptions of some of the fauna of the first five world-building periods. A knowledge of these early forms of life is not only pleasing in itself, but valuable, as giving us clearer ideas of the past ages, and because the animals and plants that then existed have a close relationship to those of our own day. The earliest animals described were the foraminifera, from which class we have our most ancient fossils. We might infer from this fact that the foraminifera were the first forms of animal life. But no; even these had predecessors, but of groups from which no fossils remain. The foraminifera, minute as they were, had shells. There is no doubt that they were preceded in the scale of creation by tiny creatures without shells, creatures that with neither arms nor legs, heads nor stomachs, yet could provide themselves with arms in an emergency, and were all mouth and stomach. Such an animal has been named a proteus from its constant changes of shape, Proteus in the classic fable being a sea-god who was constantly changing his form. The amœba, or proteus, belonged to the class protozoa, and may be described as a minute drop of a jelly-like substance, never at rest, but ceaselessly changing its shape. Imagine such a particle of jelly held suspended in a glass of water. Now it seems to extend or pour itself out on one side, into what we may call an arm, because it is reaching for an atom of food. This extended portion is drawn back, and whenever it returns into the drop, there the food is received and digested. Therefore we say the amœba is all mouth and all stomach, because it can receive and digest food in any part of its substance. The earliest of the protozoa was probably a jelly-like drop composed of a single cell. Sometimes a number of these cells, or individuals, clung together in a loosely united mass or community. When a new individual was formed the process was by “budding,” the single cell becoming two, dividing and parting, so that each individual was complete in itself; and which was the new one, and which was the old one, or whether both were part new and part old, certainly they themselves did not know. Parallel with this group of one-celled jelly-like animals, was a group of one-celled jelly-like plants. Each of these groups stood at the beginning of a great and constantly ascending series; the two groups were different in their nature and in their method of nutrition, yet each so like the other, that it is very difficult to distinguish them. Thus when we consider the dawn of life we must put the shelless protozoa ages back before the busy shell-housed foraminifera. Yet in so placing the shelless amœbæ we must not fancy them extinct. By no means: in myriad millions they still exist, and have through all the ages, and there is no pond to-day that has not its restless kaleidoscopic representatives of life’s lowest grade.