Underneath the representations of the Lares and Penates ordinarily are painted two serpents, one on either side of an altar, which they are approaching in order to partake of the offerings; these consist of fruits, in the midst of which an egg or a pine cone can usually be distinguished. As early as the beginning of the Empire the significance of the serpent in the Roman worship had ceased to be clearly understood; Virgil represents Aeneas as in doubt whether the serpent which came out from the tomb of Anchises was the attendant of his father or the Genius of the place (Aen. V. 95). In the Pompeian paintings, when a pair of serpents occurs, one may usually be recognized as a male by the prominent crest. They were undoubtedly looked upon as personifications of the Genii of the master and mistress of the house. When a single crested serpent appears, as in the shrine paintings of both the house of the Vettii (Fig. 127) and the house of Apollo (Fig. 126), we are to understand that the head of the household was unmarried. XI. SECOND STORY ROOMS With few exceptions the houses of pre-Roman Pompeii were built in only one story; where the peristyle was in two stories, there must have been rooms opening upon the upper colonnade. In Roman times, as the population of the city increased and more space was needed, it became a common practice to make the rooms about the atrium lower and build chambers over them. A complete second story was rare; small rooms were added here and there, frequently at different levels and reached by different stairways. Sometimes the second story on the front side projected a few feet over the street; an example may be seen in a house in the seventh Region (casa del Balcone Pensile), the front of which, with the part projecting over the sidewalk, has been carefully rebuilt by replacing the charred remains of the ancient beams with new timbers. Houses with three stories were quite exceptional, and the rooms of the third floor must have been unimportant. Along the steep slope of the hill, on the west and southwest sides of the city, a number of houses are found that present the appearance of several stories; they are not properly classed with those just mentioned, however, for the reason that the floors are on terraces, the highest at the level of the street, the others lower down and further back, being adjusted to the descent of the ground.