Two stages in the development of the otocyst can be recognized, the first that of an open pit FIG.
Further, two distinct types of otocyst can be recognized in the Hydro medusae; that of the Leptolinae, in which the entire organ is ectodermal, concrement-cells and all, and the organ is not a tentaculocyst; and that of the Trachylinae, in which the organ is a tentaculocyst, and the concrement-cells are endodermal, derived from the endoderm of the modified tentacle, while the rest of the organ is ectodermal.
We then find the typical otocyst of the Leptomedusae, a vesicle bulging on the ex-umbral side of the velum (figs.
In many Leptomedusae the otocysts are very small, inconspicuous and embedded completely in the tissues; hence they may be easily overlooked in badly-preserved material, and perhaps are present in many cases where they :: r simplest condition of the otocyst is a freely projecting club, a so-called (figs.
P, Pedal ganglion with otocyst attached.
U, The otocyst attached to the Ctenidium (gill-plume).
Accordingly the difference is one of position of the otocyst and not of its nerve-supply.
The right otocyst is seen at the root of the foot.
B, Trochosphere of an Opisthobranch (Pleurobranchidium) showing - shgr, the shell-gland or primitive shell-sac; v, the cilia of the velum; ph, the commencing stomodaeum or oral invagination; ot, the left otocyst; pg, red-coloured pigment spot.
In Filibranchia and many Protobranchia the otocyst (or statocyst) contains numerous particles (otoconia).
- Otocyst of Cyclas.