Abstract: To utilize the (IMP) system of temperature measure ment and the technique of tissue slice cut of the Meretrix Linnaeus and the Paphia Undulata, in three different freezing methods as -196℃(liquid), -78℃(dry ice) or -18℃(refrigerator), we have studied their tissue structural changes during the course of freezing. As a result of experiments study, the freezing in liquid nitrogen showed a little effect on the structure of the Bivalves. It was the best method best for Meretrix Linnaeus but not to the the Paphia Undulata. The method of dry ice freezing on the tissue structure of the bivalves showed some effect on the even distribution of ice crystals. The freezing method of refrigerator showed severe deformation of the tissue structural changes. Therefore, the best freezing condition for the Meretrix Linnaeus were the faster freezing velocity and the lower temperature while the best freezing conditions for the Paphia Undulata were the intermediate freezing between the dry ice and the liquid nitrogen IMP-Isolated Measurement Pod.

Key words: ice crystal, freezing, structure