What does "acephalocyst" mean?

Acephalocyst: A larval entozoön in the form of a subglobular or oval vesicle, or hy datid, 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.