Heat capacities of the binary systems consisting of a nonionic surfactant C16E8 and water were precisely measured as a function of temperature by adiabatic calorimetry over the temperature and the concentration ranges where lyotropic liquid crystals are formed. The enthalpy and entropy of transitions were determined for all known phase transitions observed. Comparison of the present result and the previous one on the C12E6-water system suggests that the higher order structure in the liquid crystalline phases in these systems be mainly constructed by surfactant molecules with a fixed amount of water. The excess heat capacities, as estimated by measuring the heat capacity of neat C16E8, are positive over the whole temperature and concentration ranges. Properties of lyotropic and thermotropic systems are compared briefly, while attention is given to the geometries of surfaces characterizing the aggregation (triply periodic minimal surface for cubic phases and flat surfaces for lamellar and smectic phases).