A, Notholca longispina, lorica only; b, Anuraea aculeata, like the former, a floating pelagic type (plankton proper); c, Synchaeta stylata; corona with accessory antennae and sensory styles; auricles for swimming - an actively swimming pelagic type (nekton); d, Pterodina patina, with bdelloid corona and retractile foot with terminal ciliated cup; e, Distyla gissensis partly extended; f, Rattulus tigris.
Near the base of the ctenidium is a patch of sensory epithelium innervated from the branchial nerve, forming a sense-organ called the osphradium, whose function is to test the water entering the branchial cavity.
There is also in some genera a median retractile sensory papilla on the dorsal posterior surface above the rectum, not covered by the cuticle.
His deduction is logical; but he has forgotten to prove the assumption, and now confuses sensory operation with sensible object.
In this tribe the males have both antennae of the first pair as sensory organs.