The inbreeding consequent upon this paucity of sponge life has produced a certain fixity of character in fresh-water sponges, and is in direct opposition to the effects of hybridization in the salt-water sponges, by which they have acquired the capacity of adapting themselves to local circumstances.

From this symbiosis there began to be formed a new people, the so-called T'u-yü-hun, a hybridization of Mongol and Tibetan stock with a slight Turkish admixture.