The Leptomedusa in form is generally shallow, more or less saucer-like, with velum less developed than in Anthomedusae (fig. 55).
In Fig. 121 I give a picture of this surface-marking of the velum.
Still watching your mouth, inhale through the nose and exhale through the mouth; see how the velum moves as you do this.
There is a veliger stage in development, but the velum is reduced.
A similar modification of the velum occurs in Dentalium and in Myzomenia among the Amphineura.
Such organs form projections on the upper surface of the velum.
At the front end of the mantle tube, which does not at first cover the velum, there is formed the foot.
Physiologically the velum is frequently important from the plexus of blood-vessels which passes with it into the III.
The edge of the disc forms a thickened ridge, the rudiment of the velum (v), which is entirely formed of epiblast.
After a little while try to move the velum, closing and opening the nose passage, without uttering a sound and without breathing.
velum ve·lum (vē'ləm)
n. pl. ve·la (-lə)
An anatomical structure resembling a veil or curtain. Also called veil, velamen.
See greater omentum.
A serous membrane or membranous envelope or covering.