On the nature of the proglottids of cestodes: a light and electron microscopic study on Taenia, Hymenolepis, and Echinococcus.

The organisation of five species of cyclophyllidean cestodes (Hymenolepis nana, H. diminuta, H. microstoma, Taenia (Hydatigera) taeniaeformis, Echinococcus multilocularis) has been studied using light and electron microscopy (SEM, TEM). It was found that there is no indication of any internal structure separating the proglottids, which are recognisable superficially. Thus in cestodes there is no metameric segmentation as in annelids. The implications of these findings on the terminology of tapeworm morphology are critically discussed.