Nereids dwell στοιχειωμένα δέντρα, ‘trees haunted by _genii_’; such innovation as there has been is in terminology only. One word of caution only is required before we proceed to the consideration of various species of _genii_ not yet described. It must not be assumed that all _genii_, on the analogy of the tree-nymphs, die along with the dissolution of their dwelling-places; the existence of the _genius_ and that of the haunted object are indeed always closely and intimately united, but not necessarily in such a manner as to preclude the migration of the _genius_ on the dissolution of its first abode into a second. The converse proposition however, that any object could enjoy prolonged existence after the departure from it of the indwelling power, may be considered improbable. The _genii_ with whom I now propose to deal fall into five main divisions according to their habitations. These are first buildings, secondly water, thirdly mountains, caves, and desert places, fourthly the air, fifthly human beings. * * * * * The _genii_ of buildings are universally acknowledged in Greece. The forms in which they appear are various; this may partly be explained by the belief that they possess the power of assuming different shapes at will; but it is certain also that their normal shape is in some measure determined by the nature of the building--house, church, or bridge--of which each is the guardian. The _genius_ of a house appears almost always in the guise of a snake, or, according to Leo Allatius[679], of a lizard or other reptile. It is believed to have its permanent dwelling in the foundations, and not infrequently some hole or crevice in a rough cottage-floor is regarded as the entrance to its home. About such holes peasants have been known to sprinkle bread-crumbs[680]; and I have been informed, though I cannot vouch as an eye-witness for the statement, that on the festival of that saint whose name the master of a house bears, he will sometimes combine services to both his Christian and his pagan tutelary deities, substituting wine for the water on which the oil of the sacred lamp before the saint’s icon usually floats, and pouring a libation of milk--for the older deities disapprove of intoxicants--about the aperture which leads down to the subterranean home of the _genius_. If it so happen that there is a snake in the hole and the milky deluge compels it speedily to issue from its hiding-place, its appearance in the house is greeted with a silent delight or with a few words of welcome quietly spoken. For on no account must the ‘guardian of the house,’ νοικοκύρης[681] or τόπακας[682], as it is sometimes called, be frightened by any sound or sudden movement. Much less of course must any physical hurt or violence be done to it; the consequences of such action, even though it be due merely to inadvertence, are swift and terrible; the house itself falls, or the member of the family who was