Goldfish embryos of pre-morula, somite formation, optic vesicle, heart formation and pigment formation stages were tested for cryoprotectant toxicity, using DMSO and glycerol at 10, 12 and 15% concentration. Those that showed 50% or more survival were employed for
cold shock test, from 24 to 4 °C at the rate of –1 °C/min. Only embryos at the heart formation stage protected with 12% DMSO showed 60% survival and 35% hatching. A group of embryos of that stage went through a freezing and thawing test to temperatures of –15, –25 and –35 °C. They showed 30, 5 and 2% survival and 12, 3 and 1% hatching respectively.