The contents of mucosubstances, proteins and lipids, and the activity of several enzymes were studied in the parenchyma of the bladder wall and the invaginated portion of Cysticercus bovis aged 108 days. The parenchyma of both parts contained a large amount of glycogen and minute bodies with a high activity of acid phosphatase and non-specific esterase. By contrast to older larvae, the young larvae contained a minute amount of hydrophobic lipids. The rostellum was developed and similar to the suckers contained glycogen.