FILIATION, civil law. The descent of son or daughter, with regard to his or her father, mother, and their ancestors.

2. Nature always points out the mother by evident signs, and whether married or not, she is always certain: mater semper certa est, etiamsi vulgo conceperit. There is not the same certainty with regard to the father, and the relation may not know or feign ignorance as to the paternity the law has therefore established a legal presumption to serve as a foundation for paternity and filiation.

3. When the mother is or has been married, her hushand is presumed to be the father of the children born during the coverture, or within a competent time afterwards; whether they were conceived during the coverture or not: pater is est quem nuptice demonstrant.

4. This rule is founded on two presumptions; one on the cohabitation before the birth of the child; and the other that the mother has faithfully observed the vow she made to her hushand.

5. This presumption may, however, be rebutted by showing either that there has been no cohabitation, or some physical or other impossibility that the hushand could be the father. See Access; Bastard; Gestation; Natural children; Paternity; Putative father. 1 Bouv. Inst. n. 302, et seq.

FILIUS. The son, the immediate male descendant. This term is used in making genealogical tables.

FILIUS MULIERATUS. The eldest legitimate son of parents, who, before their marriage, had illegitimate children. Vide Mulier.

FILIUS POPULI. The son of the people; a bastard.

FILLEY. A mare not more than one year old. Russ. & Ry. 416 Id. 494.

FILUM. The middle; the thread of anything; as filum aqua; filum viae.

FILUM AQUAE. The thread or middle of a water course. (q. v.)

2. It is a general rule, that in grants of lands bounded on rivers and streams above tide water, unless otherwise expressed, the grant extends usque ad filum aquae, and that not only the banks, but the bed of the river, and the islands therein, together with exclusive right of fishing, pass to the grantee. 5 Wend. 423.