C, A young redia, the digestive tract shaded.
D, An adult redia, containing a daughter-redia, two almost mature cercariae, and germs. E, A free cercaria.
P, Lips of redia; q, collar; r, processes serving as rudimentary feet; s, embryos; 1, trabecula crossing body-cavity of redia; u, glandular cells; v, birth-opening; w, w', morulae; y, oral sucker; y', ventral sucker; z, pharynx.
The structure of a redia, however, is an advance on that of its parent.
The movements and activity of the redia cause it to burst the wall of the sporocyst.