Phoronis muelleri (Phoronida), actinotrocha larva, telotroch and tentacles, Helgoland 06.2019. 0:48 min. Phoronis sp. starts planktonic life with tiny forms about 50 µm in length which soon develops first tentacles becoming more numerous up to 48 in some species. Old larvae reach a length of more than 1 mm. The mouth is hidden under a pre-oral lobe. Cilia on the tentacles and a heavily ciliated telotroch around the anus propel the larvae through the water. Different video-clips show different stages of development. Video can be used for teaching.