Where a bequest is made simply to a described class of persons, the thing bequeathed shall go only to such as are alive at the testator's death.

(Exception) —If property is bequeathed to a class of persons described as standing in a particular degree of kindred to a specified individual, but their possession of it is deferred until a time later than the death of the testator by reason of a prior bequest or otherwise, the property shall at that time go to such of them as are then alive, and to the representatives of any of them who have died since the death of testator.