The British legal decision in Clobberie's Case (2 Chann. Ca. 155, 2 Vent. 342, 86 Eng. Rep. 476 (1677)) established what happens when someone makes a bequest to someone and the money transfers at some point in the future and the heir survives the testator, but does not live long enough to get the money. Where there is no condition, and the money is simply to be paid at a certain time (like when the heir turns 21), then it is vested and goes to the estate if the heir survives the testator but doesn't live long enough to collect. From there it is passed through the heir's will. When there is a condition (like the heir inherits the money if they outlive Uncle Phil), then the money is conditional and if the heir doesn't meet the condition, no money is given to them or their estate, regardless of whether they survived the testator or not. The gift has lapsed. This case predated anti-lapse Statutes, but in an anti-lapse situation, the bequest to the dead heir goes to that heir's children. Unlike vesting, which goes to the heir's estate, anti-lapse money does not get probated and instead goes directly to the children (aka per stirpes), regardless of what it says in the heir's will. Whether there is a condition or not can sometimes depend on the interpretation of subtle meanings of words in the will.