- Simple tentaculocyst of Rlzopaloocellus be on the nema velatum.
This sicula, which had originally the shape of a hollow cone, is formed of two portions or regions - an upper and smaller (apical or embryonic) portion, marked by delicate longitudinal lines, and having a fine tabular thread (the nema) proceeding from its apex; and a lower (thecal or apertural) portion, marked by transverse lines of growth and widening in the direction of the mouth, the lip or apertural margin of which forms the broad end of the sicula.
In some species young examples have been met with in which the nema ends above in a small membranous disk, which has been interpreted as an organ of attachment to the underside of floating bodies, probably sea weeds, from which the young polypary hung suspended.
There is a tendency for the branches to become reduced in number, and for the serial thecae to become directed more and more upwards towards the line of the nema.
to four and these coalesce by their dorsal walls along the line of the nema, and the sicula becomes embedded in the base of the polypary.