The existence of images among the Celts as among other peoples, may owe something to the cult of trees and of stones set up over the dead. The stone, associated with the dead man's spirit, became an image of himself, perhaps rudely fashioned in his likeness. A rough-hewn tree trunk became an image of the spirit or god of trees. On the other hand, some anthropomorphic images, like the palæolithic or Mycenæan figurines, may have been fashioned without the intermediary of tree-trunk or stone pillar. Maximus of Tyre says that the Celtic image of Zeus was a lofty oak, perhaps a rough-hewn trunk rather than a growing tree, and such roughly carved tree-trunks, images of gods, are referred to by Lucan in his description of the Massilian grove.[968] Pillar stones set up over the graves of the dead are often mentioned in Irish texts. These would certainly be associated with the dead; indeed, existing legends show that they were believed to be tenanted by the ghosts and to have the power of motion. This suggests that they had been regarded as images of the dead. Other stones honoured in Ireland were the _cloch labrais_, an oracular stone; the _lia fail_, or coronation stone, which shouted when a king of the Milesian race seated himself upon it; and the _lia adrada_, or stone of adoration, apparently a boundary stone.[969] The _plurima simulacra_ of the Gaulish Mercury may have been boundary stones like those dedicated to Mercury or Hermes among the Romans and Greeks. Did Cæsar conclude, or was it actually the case, that the Gauls dedicated such stones to a god of boundaries who might be equated with Mercury? Many such standing stones still exist in France, and their number must have been greater in Cæsar's time. Seeing them the objects of superstitious observances, he may have concluded that they were _simulacra_ of a god. Other Romans besides himself had been struck by the resemblance of these stones to their Hermai, and perhaps the Gauls, if they did not already regard them as symbols of a god, acquiesced in the resemblance. Thus, on the menhir of Kervadel are sculptured four figures, one being that of Mercury, dating from Gallo-Roman times. Beneath another, near Peronne, a bronze statuette of Mercury was discovered.[970] This would seem to show that the Gauls had a cult of pillar stones associated with a god of boundaries. Cæsar probably uses the word _simulacrum_ in the sense of "symbol" rather than "image," though he may have meant native images not fully carved in human shape, like the Irish _cérmand_, _cerstach_, ornamented with gold and silver, the "chief idol" of north Ireland, or like the similarly ornamented "images" of Cromm Cruaich and his satellites.[971] The adoration of sacred stones continued into Christian times and was much opposed by the Church.[972] S. Samson of Dol (sixth century) found men dancing round a _simulacrum abominabile_, which seems to have been a kind of standing