In 1842 Danish zoologist and biologist in København Johannes Japetus Smith Steenstrup published Om Fortplantning og Udvikling gjennem vexlende Generations-raekker. In this work Steenstrup expounded the the theory of the alternation of generations, or alternation of phases or metagenesis. He showed that certain animals produce offspring which never resemble them but which, on the other hand, bring forth progeny which return in form and nature to their grandparents or more distant ancestors.
J. Norman (ed) Morton's Medical Bibliography (1991) no. 217.