acephalocyst

from The Century Dictionary.

• noun A hydatid; a member of a supposed genus Acephalocystis, instituted by Hunter for the hydatid or encysted stage of Tænia echinococcus. See Tænia.
• noun A sterile echinococcus cyst.

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

• noun (Zoöl.) A larval entozoön in the form of a subglobular or oval vesicle, or hydatid, filled with fluid, sometimes found in the tissues of man and the lower animals; -- so called from the absence of a head or visible organs on the vesicle. These cysts are the immature stages of certain tapeworms. Also applied to similar cysts of different origin.

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

• noun zoology A larval entozoön in the form of a subglobular or oval vesicle, or hydatid, filled with fluid, sometimes found in the tissues of man and the lower animals; -- so called from the absence of a head or visible organs on the vesicle. These cysts are the immature stages of certain tapeworms. Also applied to similar cysts of different origin.