Structural changes in hatching granules and behaviour of cytoplsmic inclusions in the process of hatching gland cell differentiation were studied electron microscopically using embryos of Leuciscus Hakuensis GUNTHER.
Three types of hatching granules were found in the developmental process of hatching gland cell. They were classified morphologically into type I, II and III corresponding to early, transitional and late stages of hatching gland differentiation. At the early stage of hatching gland celldevelopment, Type I hatching granules with not clear limiting membranes, inner amorphous materials, and fine mesh- like structures, well developed nucleus, mitochondria and ribosomes, and small number of endoplasmic reticulums are seen in it. At the transitional stage, type II hatching granules with clear limiting membrane and a few lamellae, and electron dense materials are seen. At the last stage, type III hatching granules was of almost the same size. The hatching granures also had limiting membranes, and were contained foamy material.