Transplantation of the lips of the blastopore in rana palustris

ROUX' first pointed out that the material which forms the embryo of the frog is laid down in the black-white ring around the equator of the egg, and that the embryo is formed by a process of concurrence in that this material grows over the white hemisphere.If this is prevented, as in his case of asyntaxia medullaris, a half embryo develops on either side of the equator of the egg.ROUX'S observations and experiments were confirmed by Morgan in a somewhat similar series of experiments.Hertwig" was able to produce the bilateral half embryos by allowing the eggs to develop in salt solutions.I have seen many similar forms from eggs of rana sylvatica and rana.palustriswhich were kept on ice for a prolonged period of time.I n such abnormal forms the lips of the blastopore which fail to grow over the large yolk plug differentiate into these modified half embryos with a central nervous system, muscle, the chorda, and the roof of the archenteron.More recently Morgan has investigated the question of the location of the embryo-forming substances and concludes that the material is first in the upper hemisphere of the developing frog's egg and is later carried downward into the germ ring.