The dissociated early embryonic cells of the fresh water fish, Oryzias latipes, protrude hyaline lobopodia, which tend to rotate around the cell circumference in a propagating wave. Cells from late blastula or gastrula continuously show this “circus movement”, while most cells up to early blastula are rounded. The linear velocity of the lobopodium was estimated by means of time-lapse cinemicrography. The velocity increases slightly as cell diameter increases. The effects of pH, temperature and osmotic pressure of the immersion media on the movement were also quantitatively investigated. Cells become rounded and do not form lobopodial blebs when immersed in media below pH 5. The velocity is reduced by decreasing temperature, but the movement continues even at 5 degrees C. Cells placed in hypertonic salt solutions become crenated and do not continuously demonstrate the circus movement.

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