Figure 1.
External appearances (a, c, e, g) and histological features (b, d, f, h) of the early embryos of Rana rugosa. Fertilized eggs were developed to the neurula (a, b) at two days after fertilization (DAF) and the embryos at stages 21 (c, d), 24 (e, f), and 25 (g, h) of Shumway (43) at 4, 6, and 8 DAF, respectively. At 2 DAF, the chemical treatments were terminated. Hatching occurred at 3 DAF. Two external gills can be seen at both sides of the embryo at stage 21 (c), and thereafter only one gill disappears in the embryo at stage 24 (e). A mass of cells containing yolk can be seen in the abdominal region of the neurula (b), and thereafter this diminished in the embryos during development (d, f, h). Organs such as the pronephros, heart, liver, and intestine, are differentiated in the embryos during development (d, f, h). Scale bar=2 mm.