Anterior limb buds from the 11-day-old mouse embryos were cultivated for 24 hours in a chemically defined medium or in chemically defined medium with biologic supplements using the agar culture method for the purpose of comparison among those media.
1. In Medium 199, scarcely any growth or histological diff e rentiation was observed.
2. It w as revealed that the biologic supplement,, i. e., chick embryo extract or horse serum, was necessary for the development of limb bud and the differentiation of mesenchyme into cartilage.
3. The three media, Medium 199 with chick embryo extract, Medium 199 with horse serum and Medium 199 with chick embryo extract and horse serum, gave almost the same results. In the former two media, the differentiation of mesenchyme into cartilage was more advanced, while in the latter media, the digital rays developed more frequently with the thining-out of mesenchyme.

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On human permanent teeth excepting the molars, the author observed the perikymatien stained with hematoxylin and counted the number of perikymatien on the four dental surfaces, downwards from a standard perikymata which is well observable on all the four surfaces without discontinuity. The results obtained are as follows:
1. T he perikymatien did not run around the crown in parallel to the cervical line, but they were interrupted by the cervical line on the proximate surfaces and by the lakes in the enamel.
2. Therefore, the formation of the enamel wa s not completed simultaneously on all the four dental surfaces. There was a regularity in the order of crown completion according to each dental species.
3. The crown formation in the incisors was completed in order on the mesial, distal, labial and lingual surfaces. In the canine and the second premolar, the order is on the mesial, distal, lingual and labial surfaces. In other words, the order of crown completion in regard to the labial and lingual surfaces in the incisors was reversed in the canine and first and second premolars. Only in the first premolar was the crown formation completed later on the mesial surface than on the distal surface.
4. Concerning the order of crown completion among the four dental surfaces, there was no sexual difference or difference between the right and left sides.

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For the investigation of t h e morphology and architectonics of the glial cells in the chicken brain and spinal cord, the author observed first the glial cells in the optic tract, where no nerve cell bodies occur, staining with hematoxylin and other routine stainings for the nuclei of glial cells and with various kinds of silver impregnation methods for the cell body and processes of the glial cells.
The morphological characteristics of glial cells in th e chicken optic tract, which were stained with silver impregnation methods, were classified into four types of fibrous astrocyte, oligodendroglia, microglia (lamellar form) and unknown type of glial cells as in the white matter of mammals.
Though the types of glial cells which were stained satisfactorily were more or less different according to kinds of silver impregnation methods employed, the characteristics of silver impregnated images of each type of glial cells scarcely showed a difference.
According to the nuclear structures of glial cells, they were classified into four types. The three types were considered to correspond to astrocyte, oligodendroglia and microglia respectively which were seen in silver impregnated materials, and the fourth type of glial nuclei was small and chromatin-rich, and might be immature glial cells as described by Smart and Leblond (1961). In the optic tract the glial cells consisted chiefly of oligodendroglia (so-called interfascicular glia) and they were arranged in various length of rows between nerve fibers. The glial cells were also found along small blood vessel walls in a long line in the stratum opticum or in a short line in the optic chiasm and its neighbouring region. In the optic chiasm and its neighbouring region the numerous glial cells were occasionally found to form clusters around the small blood vessels. These groups consisted of numerous oligodendroglia and a few of astrocytes and microglia.

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