/awr'theuh jen"euh sis/ , n.
1. Biol.
a. Also called orthoselection . evolution of a species proceeding by continuous structural changes in a single lineage without presenting a branching pattern of descent.
b. a theory that the evolution of a species in a continuous, nonbranching manner is due to a predetermined series of alterations intrinsic to the species and not subject to natural selection.
2. Sociol. a hypothetical parallelism between the stages through which every culture necessarily passes, in spite of secondary conditioning factors.
[ 1890-95; ]