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.
Sociology. a hypothetical parallelism between the stages through which every culture necessarily passes, in spite of secondary conditioning factors.
Main Entry: or·tho·gen·e·sis Pronunciation: "or-th&-'jen-&-s&s Function: noun Inflected Form: pluralor·tho·gen·e·ses/-"sEz/ : variation of organisms in successive generations that in some evolutionary theories takes place in some predestineddirection and results in progressive evolutionary trends independent of external factors —or·tho·ge·net·ic/-j&-'net-ik/adjective
[awr-thuh-jen-uh-sis] 
θəˈdʒɛn