The heat capacity in the isotropic phase and the latent heat on the IN transition line have been measured in binary liquid crystal mixtures by high-resolution adiabatic calorimetry. It shown that an anomalous behaviour of the entropy jump on the IN phase transition line in the vicinity of the INA triple point is defined only by an particular behaviour of the crystallization fluctuations in the isotropic phase. The contribution of the crystallization fluctuations to the heat capacity is comparable with the pretransitional heat capacity of the nematic fluctuations in the isotropic phase.