Hatschek (1888) treated the Entoprocta as a division of his group Scolecida, characterized by the possession of a primary body-cavity and of protonephridia; while he placed the Ectoprocta, with the Phoronida and Brachiopoda, in a distinct group, the Tentaculata.
Against this view may be urged the essential similarity between the processes of budding in Entoprocta and Ectoprocta (cf.
The fresh-water fauna also contains a representative of the Entoprocta (Urnatella), two or three Ctenostomes, such as Victorella and Paludicella, and one or two species of Cheilostomata.
In other Entoprocta the buds on a horseshoe retain a high degree of individuality, a shaped l o p h o - thread-like stolon giving off the cylindrical phore; stalks, each of which dilates at its end i, Ectocyst; into the body of a zooid.
While the mouth is invariably encircled by the bases of the tentacles, the anus lies within the series in the Entoprocta and outside it in the Ectoprocta.
In the Entoprocta the tentacles are withdrawn by being infolded into the "vestibule," a depression of the oral surface which can be closed by a sphincter muscle.
The development of the Ectoprocta is intelligible on the hypothesis that the Entoprocta form the starting-point of the series.
- For general accounts of the structure and development of the Polyzoa the reader's attention is specially directed to 12, 14, 6, 25, I, 2, 17, 26, 18, 23, 3, in the list given below; for an historical account to i; for a full bibliography of the group, to 22; for fresh-water forms, to 1-3, 7-10, 17; for an indispensable synonymic list of recent marine forms, to 15; for Entoprocta, to to, II, 24; for the classification of Gymnolaemata, to 21, 1 4, 4, 13, 20; for Palaeontology, to 27, 22.