The second is the number of generations or births, and presides over them in the same mysterious manner in which the stars preside over them, or in which, according to the Pythagoreans, opportunity, justice, marriage, are represented by some number or figure.

This is probably the number 216.
The explanation given in the text supposes the two harmonies to make up the number 8000.

This explanation derives a certain plausibility from the circumstance that 8000 is the ancient number of the Spartan citizens (Herod.), and would be what Plato might have called 'a number which nearly concerns the population of a city'; the mysterious disappearance of the Spartan population may possibly have suggested to him the first cause of his decline of States.

The lesser or square 'harmony,' of 400, might be a symbol of the guardians,--the larger or oblong 'harmony,' of the people, and the numbers 3, 4, 5 might refer respectively to the three orders in the State or parts of the soul, the four virtues, the five forms of government.

The harmony of the musical scale, which is elsewhere used as a symbol of the harmony of the state, is also indicated.