sporocyst

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A resting cell that produces asexual plant spores.
• noun A protective structure containing the infective sporozoites of an apicomplexan parasite.
• noun A saclike larval stage in many trematodes, from which the rediae emerge.

from The Century Dictionary.

• noun In zoology: The cyst, sac, or capsule which is developed in the process of sporular encystment; any unicellular organism which becomes encysted and proceeds to sporulation.
• noun A cyst or sac containing spores or germs, such as is developed in the larval state of certain flukes, or trematoid worms, as Bucephalus; this state of such worms; a redia containing cercariæ. See redia, and cuts under cercaria, germarium, and Trematoda.
• noun In botany, a unicellular alga which, usually by a process of division, produces only asexual spores: in contrast with sporangium, which is usually limited to multi-cellular organs producing asexual spores.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Zoöl.) An asexual zooid, usually forming one of a series of larval forms in the agamic reproduction of various trematodes and other parasitic worms. The sporocyst generally develops from an egg, but in its turn produces other larvæ by internal budding, or by the subdivision of a part or all of its contents into a number of minute germs. See redia.
• noun (Zoöl.) Any protozoan when it becomes encysted and produces germs by sporulation.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun biology A cyst that develops from a sporoblast and from which sporozoites develop
• noun A larval stage in many trematode worms