miracidium of Megalodiscus temperatus from Rana pipiens. This section reveals two of the glands used in penetration of the snail host.  The upper gland is one of four penetration glands with its own unique secretory granules (SG).  The lower gland is the secretory sac (SS) with its secretory bodies (SB).  Note also the nucleus of the penetration gland (NUP) and ribosomal endoplasmic reticulum (RER).  38,000x