referenceID fullReference Ehlers Ehlers U. Das Phylogenetische System der Plathelminthes. Stuttgart: Gustav Fischer; 1985. Lanfranchi Lanfranchi A. Ultrastructure of the epidermal eyespots of an acoel platyhelminth. Tissue & Cell. 1990;22(4):541–546. doi: 10.1016/0040-8166(90)90082-K Yamasu Yamasu T. Fine-structure and function of ocelli and sagittocysts of acoel flatworms. Hydrobiologia. 1991;227:273–282. doi: 10.1007/BF00027612. Achatz Achatz JG, Hooge M, Wallberg A, Jondelius U, Tyler S. Systematic revision of acoels with 9 + 0 sperm ultrastructure (Convolutida) and the influence of sexual conflict on morphology. Journal of Zoological Systematics and Evolutionary Research. 2010;48(1):9–32. doi: 10.1111/j.1439-0469.2009.00555.x. Hooge Hooge MD, Tyler S. New tools for resolving phylogenies: a systematic revision of the Convolutidae (Acoelomorpha, Acoela) Journal of Zoological Systematics and Evolutionary Research. 2005;43(2):100–113. doi: 10.1111/j.1439-0469.2005.00301.x. Popova Popova NV, Mamkaev YV. Ultrastructure and primitive features of the eyes of Convoluta convoluta (Turbellaria Acoela) Doklady Akademii Nauk SSSR. 1985;283(3):756–759. Tekle Tekle YI, Raikova OI, Ahmadzadeh A, Jondelius U. Revision of the Childiidae (Acoela), a total evidence approach in reconstructing the phylogeny of acoels with reversed muscle layers. Journal of Zoological Systematics and Evolutionary Research. 2005;43(1):72–90. doi: 10.1111/j.1439-0469.2004.00293.x.