Abstract: A closed end surgical cryoprobe instrument with probe shaft diameter of 3 millimeters or less is made to achieve and maintain freezing zone temperatures close to that of the liquid cryogenic refrigerant. Using sub-cooled liquid nitrogen at approximately -208.degree. C. freezing zone temperatures as low as -206.degree. C. can be achieved in under 1 minute. The liquid nitrogen supply tube is provided with a plurality of small vent holes to vent gas formed or present in the refrigerant supply tube to the return refrigerant flow channel. The vent holes also allow small amount of liquid nitrogen to vent into the return flow channel to further reduce the temperature differential between the sub-cooled liquid nitrogen supply and the counter-current flowing return refrigerant.

Abstract: A method for the cryopreservation of multicellular organisms characterized by rapid cooling and warming rates, exceeding 100.degree. C. per minute, to achieve 80% survival after storage in the frozen state. The method involves exposing multicellular organisms to a cryoprotectant medium, freezing the organisms and medium by cooling at a rate greater than 100.degree. C. per minute, holding the organisms and medium at a point below 0.degree. C. for a period of time, and cooling the organisms and the medium at a rate greater than 100.degree. C. per minute to an appropriate storage temperature depending upon the desired length of the storage period. The method is more specifically described with regard to aquatic organisms, and particularly described with regard to the cryopreservation of immature marine crustaceans.