The spiral ridge figured by Hertwig (Fig. 61, 1. c) is probably an incorrect representation of this structure, exceedingly minute in all genera but Choanophrya.
In Choanophrya I have failed to find any pore, and believe the bud-formation to be strictly endogenous.
See Quart. Journ. Micr. Sc. xlv. 1902, p. 325.
In Journ. Coll. Sc. Japan, x. 1896.
Étude monographique sur le groupe des Tentaculifères, Ann. Soc. Belge Micr. xxiv.-xxvi. 1901.