Figure 3.

Embryonic development of hybrids and parental crosses. Embryonic development of perch from different crosses. A) Embryos from a parental population (eastern population), four days after fertilization. B) Egg-strand of cross F₁1, female eastern/male western population, 10 days after fertilization. rh = ready to hatch embryos, ded = embryos with disturbed embryonic development, ue = unfertilized eggs. C) Egg-strand of cross F₁2, female western/male eastern population, one day after hatching. de = dead embryos of different embryonic stages, ee = empty egg shells that remained after hatching.