We have dealt mainly with _Amoeba_, _Hydra_, and the ant-community which exemplify three somewhat distinct types of organic individuality. Some of the transitional forms have been specified to show how the second kind originates from the first, and how in its turn this grows in time into the third and most complex association; thus _Vorticella_ and _Volvox_ connect _Amoeba_ with the cell-community individual like _Hydra_ and a solitary wasp, while the annually established colonies of social wasps and of bumblebees lead to the permanent colony-individual. Restricting attention to the three primary examples, and remembering that the criterion of completeness is the ability to discharge satisfactorily all of the eight biological tasks, it is clear that the entire _Hydra_ and the whole ant-community correspond _physiologically_ with _Amoeba_, although the first-named is _structurally_ a cell-community equivalent to many protozoa, and the insect colony is composed of many such cell-communities as elements. In the third type, neither a single queen nor a single worker is able to carry on all of the biological tasks any more than a muscle-cell or an unformed egg of _Hydra_ can maintain itself capably in isolation. Therefore the ant-society as a whole and the _Hydra_ in its entirety are organic individuals on the same physiological plane with _Amoeba_, and they are equally subject to the same great laws of nature demanding selfish maintenance and racial perpetuation. But we must not lose sight of the fundamental value of the unit during the evolution of a higher from a lower type. The tissue-cell of _Hydra_ must still obey the mandate to live an efficient personal life, because this is necessary for the welfare of other cells and of the whole complex. The original egoistic tasks are not abolished, but new duties are added to them in ways we have learned to distinguish. In _Vorticella_ the products of fission do not separate, and certain advantages accrue from the organic continuity thus maintained. The success of _Hydra_ in its ceaseless struggle to live depends wholly upon the cooperation of its differentiated cell-units, now no longer equivalent in function to the all-powerful _Amoeba_, although each one must be kept alive until its task is done, or the whole association would have no place in nature. Similarly in the higher insect community, the superadded duties to fellow-components are even clearer, for in the competition of colony with colony, involving terrific battles whose casualties may be numbered by thousands, the stronger wins; and strength depends upon the concerted efforts of all the members of the kingdom, that only collectively constitute a complete biological whole. Mere self-protection demands altruistic conduct: if the worker ceased to bring in food when its own hunger was satisfied, there would be no tribal stores for the stay-at-home queens and nurses; and if