We see, then, that from ancient times there were among the Aryas families in possession of effectual invocations of the gods, who knew how to pronounce and sing the prayers at sacrifice, and offer the sacrifice in due form. We may gather further from the Rigveda that these families were distinguished by special symbols. The family of Vasishtha had a coil or knot of hair on the right side,[50] the family of Atri had three knots, the family of Angiras five locks, while the Bhrigus shaved their hair.[51] Sung for centuries in these families, in these circles of minstrels and priests, these poems were thus revised and preserved, until at length out of the possessions of these schools arose the collection which we have in the Rigveda. We find frequent mention in the poems of the invocations of ancient time, of the prayers of the fathers, and hence what is in itself probable becomes certain--that we have united in the Rigveda poems of various dates, and invocations divided in their origin by centuries. Though the minstrels of the poems of the Rigveda could look back on a distant past, though they could distinguish the sages of the ancient, the earlier time, and the present, and the men of old from those of the later and most recent times,[52] there is yet nothing in these poems to point to an earlier home, to older habitations, or previous fortunes of the nation, unless, indeed, we ought to find an indication of life in a more northern region in the fact that the older poems in the collection count by winters, and the later by autumns.[53] In any case there is no remembrance of earlier abodes, and therefore we must conclude that even the oldest of these poems had been sung long after the immigration. If the assumption established above, that the immigration took place soon after 2000 _B.C._, is approximately probable, the extinction of any memory of earlier abodes and fortunes will hardly allow us to carry back the origin of the oldest songs of the Veda beyond the sixteenth century _B.C._