The Gastrulation of the Egg of Bufo lentiginosus

AN examination of the literature dealing with the early development of the amphibian egg shows many conflicting observations and theories regarding the origin of the blastopore and the manner of formation of the mesoderm and notochord. It is evident, therefore, that more forms must be studied and the observations in some cases carefully repeated before any general conclusions regarding the origin of these structures can be drawn for the entire group. The amphibian eggs that have been most studied are those of Rana, Triton, Axolotl, and Bombinator. The present paper deals with the early development of the egg of Bufo lcnt1zr<inlosuls from the end of cleavage until the closure of the blastopore. The eggs of this amphibian, although very abundant and easily obtained, have been but little used either for observation or for experiment, owing, doubtless, to their small size and to their relatively deep pigmentation, which makes it very difficult to follow the fate of living cells.