Juveniles are more translucent than adults so the internal eye at the base of each rhinophore is more visible. The translucent, whitish cnidosacs (1) inside the distal tips of cerata are not obscured by the incompletely developed, opaque, white, subapical ring (2) and the rhinophores are whitish.
Length 5 mm. Mersey Estuary, England. September 2010.