"When we see human parents, see human woman pregnant out in public, we find it odd and some unpleasant. Breeders should be in den. We think, how strange you treat your breeders — and then we remember, all you are breeders. 'Wife, husband, mother, father.' We do not think in such ways."

A sept was a division of a clan of infertile Selonian females who shared the same father and breeder mother.

The vast majority of the Selonian population consisted of infertile females, who functioned as the workers of the species. The few males and breeder females were very well protected, but were not allowed to leave their dens. Within a den, the single breeder female would mate with a handful of males and give birth to a brood of Selonian children by each. Each breeder male thus fathered a subset of the population of the den, and these subsets with the same father were referred to as 'septs.'

There was little genetic difference between Selonians of the same den. To outsiders they appeared identical. Within the same sept there was even less difference. Sisters of the same sept, who could number in the hundreds or thousands, were virtually identical, differing only in the tasks assigned to them by the den and acquired personality traits.

Selonians had a difficult time grasping the concepts of family for most humanoids, especially more distant relations such as 'uncle' or 'cousin.' In Human terms, two Selonian females of the same den but different septs would be half-sisters.