serve as animated preserve jars, distended sometimes to the size of a grape with the communal stores of food, which they return to the workers when external sources of food may fail.  Finally there are the slaveholding species which conduct forays upon the nests of other forms, to procure the young of the latter, which grow up in their captors’ nests and serve them as nurses and masons and foragers.  So long has this custom been established that some slaveholders are entirely unable to feed themselves, and would die out if their slaves failed to support them.

* * * * *

Let us pause at this point to summarize the results of the foregoing analysis, in order that we may approach the biological study of human associations with definite and clear conceptions of the fundamental laws controlling living communities of all grades.

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