They were a hostile race, but the hostility was felt and expressed on religious rather than racial grounds, as the latter term is understood at present.
12.

The Sudra.
M.Senart points out that the division of the four castes appearing in post-Vedic literature, does not proceed on equal lines.

There were two groups, one composed of the three higher castes, and the other of the Sudras or lowest.

The higher castes constituted a fraternity into which admission was obtained only by a religious ceremony of initiation and investment with the sacred thread.

The Sudras were excluded and could take no part in sacrifices.