On the Sporocyst and Cercaria of a Marine Distomid Trematode from Nucula

Abstract
The cercaria is liberated from an unbranched sporocyst by the birth-pore. It is spindle-shaped and possesses a bifid tail. It possesses two suckers, a long oesophagus and a forked gut. The excretory vesicle is Y-shaped with two furcal extensions from its stem. The cuticle is unarmed. There is no stylet or cystogenous organ.There is no redia.All stages in the development of the cercaria are found within the sporocyst.