If human ethics is truly unrelated to beginnings found in lower nature, something that has arisen by itself from supernature, then we must not use the terms in question except by way of analogy. If, however, nature has been continuous in the working out of every department of human life and human thought through evolution, then the criteria of the righteousness of the acts performed even by an _Amoeba_ may be found to be basic and fundamental for ethical systems of whatever human race or time. This subject remains to be discussed in the final chapter, but it must be clear that we cannot survey the evolutionary process by which social systems have come into being without dealing at the same time with the origin and growth of ethical conduct as such.
Without leaving the group of one-celled animals typified by _Amoeba_, we find colonies of the most elementary biological nature, where other natural obligations are added to the two of greatest importance. Some species of the bell-animalcule, _Vorticella_, provide characteristic examples of these primitive compound protozoa. Here the assemblage is made up of one-celled individuals essentially similar to one another in structure and in physiological activities; in the latter respect each one of them is like _Amoeba_ as well. They may remain together for a longer or shorter period, or during their whole existence until the time of reproduction. Like the solitary protozoön, each member leads a complete life in and by itself, equivalent to that of every biological unit. It obeys the two great laws already laid down, but in addition it seems to be required to remain with the others for some mutual good. The biological value of the association which imposes this additional obligation may be found perhaps in the fact that a large group is not so readily eaten by an enemy as an individual cell; but it is clearer that the process of reproduction, which consists of the fusion of small "gametes," or nucleated fragments produced by diverse or similar parents, must be greatly facilitated by the occurrence of gamete-forming individuals in one and the same colony. "_To remain together_" is the new duty imposed by nature for the good of all and for the welfare of each member of the group. Some biological advantage accrues to the several components, just as the banding of wolves enables the pack to accomplish something which the single wolf is unable to do, although in the latter case it is not so much a reproductive alliance that is formed as an offensive and defensive union.