An electron microscope study of the tegument and associated structures of Dipylidium Caninum By L. T. THREADGOLD

The ultrastructure of the 'cuticle' of Dipylidium caninum is described. The presence of mitochondria within the 'cuticle' and the connexion between it and subcuticular cells indicates that the outer covering of this cestode is of living cells forming an epidermis. On its external surface the epidermis is folded into finger-like microthriches and its thickness is pierced in places by pore-canals ending at the basement membrane. The sunken epidermal cells contain mitochondria, endoplasmic reticulum, fatty or glycogen inclusions, and protein crystalloids. It is suggested that such cells act as both storage and synthesizing units. The possible bearing of the present morphological findings on cestode physiology is discussed, especially in reference to cestode resistance to digestion and the ability of the 'cuticle' to absorb.