Notes from synonyms
Diagnosis for Acoela Polycanthiidae
Hooge MD 2003 (citation) - Male copulatory organ a multi-layered seminal vesicle composed of five layers of alternating longitudinal and circular muscles: outer-longitudinal muscles, outer-circular muscles, middle-longitudinal muscles, inner-circular muscles, and inner-longitudinal muscles. Epithelium-lined lumen of seminal vesicle opens proximally to false seminal vesicle and distally to ciliated male antrum and terminal male gonopore. Invaginated penis absent.
Diagnosis for Acoela HaploposthiidaeWestblad E 1948 (citation); see also Dörjes (citation) - Acoels with simple copulatory organs. In most cases this organ consists of a tube-shaped male antrum and a spherical seminal vesicle. Either the antrum or the seminal vesicle or both can be absent. Penis is lacking [but Haploposthia albiventer Marcus and H. rubra (An der Lan) have a very small penis papilla]. Male gonopore terminal, subterminal, or ventral. Mouth ventral.
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