Figure 2.

Evolutionary distance tree. Based on the neighbor-joining method including the complete 18S ribosomal RNA sequences of 33 species belonging to 16 different phyla, with special emphasis on platyhelminths. The nemertean listed is Prostoma eilhardi. The numbers at the nodes are percentages of 1,000 boot trap replicates that support the branch, with only values over 50% being represented. All branch lengths are drawn to scale. The choanoflagellate Sphaeroeca volvox is used as outgroup. The Fitch–Margoliash method gives the same topology. (Reproduced with permission from ref. 27.)