1. Certain starch grains and the polyhedral bodies of insects are hexoctahedra of the type described by Lewis for tissue cells and coagulated yolk, and by Kelvin in systems of soap bubbles. 2. Compression of units visible in cellular emulsions results in aggregates of hexoctahedra. Under the same conditions the same form is postulated as either imminent or actual, at levels below the limits of visibility. 3. If this extension applies to materials that control the dimensions of organisms, Marvin's hexoctahedral aggregation series should be capable of replacing either organic correlative in the heterogonic equation y = bxkh. Evidence is afforded by heterogonic curves in which the Marvin series is plotted against the chick embryo and the chlorides of the chick embryo. 4. The success of this test depends on two facts: (a) the heterogonic constant is the ratio between two growth constants; and (b) when isogonic aggregates of hexoctahedra are produced by organic growth, the number of layers in which the resulting units stack about a central unit, is proportional to time.