In elementary school science textbooks, the study unit "animal birth" has an activity to observe the embryogenesis of medaka (Oryzias latipes) while in the egg. It is important to understand this process not in isolation, but continuously. Elementary school children cannot recognize embryonic development correctly while they intermittently observe living embryos selected randomly from adult medaka or attached on waterweeds growing in an aquarium. Some supplementary teaching materials are

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... d in observing living embryos to understand the morphogenetic process continuously. In this study, we observed the development of medaka and prepared fixed specimens of embryos, allowing their developmental stage to be observed at any time. First, we investigated whether college-level students could observe the organs and structures of fixed embryos the same as for living embryos in order to evaluate the applicability of the fixed embryos before trying to use the embryo specimens with elementary school children. The structures of the living embryos such as the blood, blood vessels, and heart, for which movements can be easily observed were better recognized compared with the fixed embryos, but there was no significant difference between the recognition of other organs and structures of living and fixed embryos. We also implemented the observation of medaka embryos in elementary school science classes with fixed embryo specimens which can show the sequence of embryonic development and we considered their utility. As a result, in the class using the fixed embryos as supplementary teaching materials along with living embryos, more children were able to recognize correctly either the days after oviposition or the process in which the body was developing, compared with the class using only textbooks. Therefore, we suggest that the use of fixed embryo specimens, along with living embryos, helps children to comprehend better the embryogenesis of medaka than the use of only textbooks does.