As to external form, the various shapes of the more primitive dragons have been largely determined by the mythologic currents amid which they have fallen, though their original basis in nature may generally be traced. In the far North, where the legends of swan-maidens, pigeon-maidens, and vampyres were paramount in the Middle Ages, we find the bird-shaped dragon very common. Sometimes the serpent-characteristics are pronounced, as in this ancient French Swan-Dragon (Fig. 26); but, again, and especially in regions where serpents are rare and comparatively innocuous, the serpent tail is often conventionalised away, as in this initial V from the Cædmon Manuscript, tenth century (Fig. 27), a fair example of the ornamental Anglo-Saxon dragon. The cuttlefish seems to have suggested the animalised form of the Hydra, which in turn helped to shape the Dragon of the Apocalypse. Yet the Hydra in pictorial representation appears to have been influenced by Assyrian ideas; for although the monster had nine heads, it is often given seven (number of the Hathors, or Fates) by the engravers, as in Fig. 6. The conflicts of Hercules with the Hydra repeated that of Bel with Tiamat ('the Deep'), and had no doubt its counterpart in that of Michael with the Dragon,--the finest representation of which, perhaps, is the great fresco by Spinello (fourteenth century) at Arezzo, a group from which is presented in Fig. 28. In this case the wings represent those always attributed in Semitic mythology to the Destroying Angel. The Egyptian Dragon, of which the crocodile is the basis, at an early period entered into christian symbolism, and gradually effaced most of the pagan monsters. The crocodile and the alligator, besides being susceptible of many horrible variations in pictorial treatment, were particularly acceptable to the Christian propaganda, because of the sanctity attached to them by African tribes,--a sanctity which continues to this day in many parts of that country, where to kill one of these reptiles is believed to superinduce dangerous inundations. In Semitic traditions, also, Leviathan was generally identified as a demonic crocodile, and the feat of destroying him was calculated to impress the imaginations of all varieties of people in the Southern countries for which Christianity struggled so long. This form contributed some of its characters to the lacertine dragons which were so often painted in the Middle Ages, with what effect may be gathered from the accompanying design by Albert Durer (Fig. 29). In this loathsome creature, which seeks to prevent deliverance of 'the spirits in prison,' we may remark the sly and cruel eye: the præternatural vision of such monsters was still strong in the traditions of the sixteenth century. In looking at this lizard-guard at the mouth of hell we may realise that it has been by some principle of psychological selection that the reptilian kingdom gradually gained supremacy in these portrayals of the repulsive.