they are far from meaning that during a long course of descent, primordial organs of any kind-vertebrae in the one case and legs in the other-have actually been converted into skulls or jaws.
ez dute esan nahi, ezta urrunetik ere, ondorengoen hurrenketa luze baten buruan edozein motatako organo funtsezkoren batzuk-zenbait kasutan ornoak eta beste zenbaitetan hankak-benetan ere burezur edo baraila bihurtu direnik.