Anton Dohrn and the problems of 19th century phylogenetic morphology

According to Anton Dohrn, evolutionary development was performed in a single progressive lineage where some proto-annelid initiated an evolutionary development that went straight on via annelids and lower vertebrates to man. From that line, a kind of metamorphosing nature, certain branches were derived, like protists or worms or even tunicates, which Dohrn thought off as degenerating groups. With that concept Dohrn came close to typological ideas of his time. Nevertheless, recent evo-devo literature seems to be influenced by Dohrn's outline of evolution.