A structure which has been developed through long-continued selection, when it ceases to be of service to a species, generally becomes variable, as we see with rudimentary organs;
Hautespen jarraikiz luzaro garatu den egitura bat, espezie batentzat baliagarri izateari uzten dionean, eskuarki aldakor bihurtzen da, aztarna-organoetan ikusten dugun moduan, aurrerantzean ez baitu hura hautespen indar berak erregulatuko.