FIG. 1. AMŒBA PRINCEPS, IN DIFFERENT FORMS.
Let us take the lowest of these lowly creatures, the amœba, or proteus, which we may find during the summer in almost every fresh water pond. I cannot describe it, for, like its namesake, it is constantly changing its form, slipping away from us, as it were, right before our eyes, and assuming a new shape. As Proteus of old could assume any form, either plant or animal as he pleased, so our amœba can assume various forms at pleasure.
You will remember that Homer introduces Proteus in the fourth book of the Odyssey. He makes him the servant of Neptune, and says his office was to take care of the seals or sea-calves. And who knows but his namesake may have some such office among the curious beings of the microscopic world which is peopled with as many strange creatures as those we read of in ancient mythology?
We frequently see our proteus adhering to a leaf of some water plant when it looks like a little ball of jelly; and while we are looking at it, it pushes out an arm here, and now another there, and still another, as if feeling for something. (Fig. 1, Amœba princeps.) Not finding anything to its taste, it moves or crawls along with its temporary arms extended—all the while changing them, throwing one out on this side, then on that, then contracting and pushing out in another place. It seems to be actively in search of something. At last it has reached a moving diatom with one of its long arms, which it immediately wraps around it, and now the other arms are contracted and the creature actually folds itself around its dinner! He turns himself outside in, and makes a temporary stomach, and proceeds to digest the soft parts of the diatom. After he has extracted all the nourishing part, he squeezes or pushes out the clear, transparent shell, and starts in search for something more.
It is not known to a certainty how the amœbæ are produced, but this much is known: If a portion of the body is detached from the rest, it does not die, but becomes an independent amœba. If a portion of one of the arms becomes separated from the main body, it does not seem to incommode the creature in the least, and the small part soon begins to extend tiny arms and behave in every way like its parent. And this may be the only way in which the children of Proteus are made—veritable children of his own flesh.
How strange it seems that a jelly-like mass of substance without form or organization should be endowed with life and sufficient sense to go in search of food and have the power of selection.
Life manifested in the lowest animal or plant is just as wonderful and hard to understand as that which pervades the higher animals.
Some of the species of the fresh water amœba live in shells of various forms and patterns. One which we often see has a little house made of tiny particles of sand and minute bits of shell soldered together with a kind of cement which hardens in water; these are vase or pitcher-shaped and always look rough on the outside.
FIG. 2. TESTACEOUS FORMS OF AMŒBAN RHIZOPODS.