The Collaborative International Dictionary of English v.0.48:

Digenesis \Di*gen"e*sis\, n. [Pref. di- + genesis.] (Biol.)
   The faculty of multiplying in two ways; -- by ova fecundated
   by spermatic fluid, and asexually, as by buds. See
   Parthenogenesis.
   [1913 Webster]

WordNet (r) 3.0 (2006):

digenesis
    n 1: alternation of sexual and asexual generations [syn:
         metagenesis, digenesis]