Fig 4. Quadratic regression lines between incubation time and development of the primitive streak in Taiwan Country Chicken (TCC) and Brown Tsaiya Ducks (BTD).

The developing primitive streak of embryos in BTD (blue dot line; y = -0.002x² + 0.1079x - 0.6786 R² = 0.8716) and TCC (red dot line; y = -0.0026x² + 0.0985x + 0.1585 R² = 0.7266) can be well-represented with each quadratic regression line. Values are presented as mean ± SD in both species.