. The biology of the amphibia. Amphibians. THE INTEGUMENT 131 determined very early and is continued even when the ectoderm is isolated from the underlying tissues (Twitty, 1928). Unicellular Glands.—Shortly before hatching, a series of uni- cellular glands appear on the snout of tadpoles and probably all urodele larvae. They may extend along the back of some frog embryos (Saguchi, 1915). In Xenopus (Bles, 1906), Alytes. Fig. 48.—The hatching of Alytes, the midwife toad. As in the case of other Salientia, the tadpole escapes from the egg by digesting its way out. A. Section of the frontal orga
. The biology of the amphibia. Amphibians. THE INTEGUMENT 131 determined very early and is continued even when the ectoderm is isolated from the underlying tissues (Twitty, 1928). Unicellular Glands.—Shortly before hatching, a series of uni- cellular glands appear on the snout of tadpoles and probably all urodele larvae. They may extend along the back of some frog embryos (Saguchi, 1915). In Xenopus (Bles, 1906), Alytes. Fig. 48.—The hatching of Alytes, the midwife toad. As in the case of other Salientia, the tadpole escapes from the egg by digesting its way out. A. Section of the frontal organ or digesting glands just before hatching. B-E., Several stages in the hatching process; , hatching gland cell; , supporting cell. (Noble, 1926), the axolotl (Wintrebert, 1928), and Ambystoma opacum (Noble and Brady, 1930), it has been shown that these glands function in producing a secretion which digests the egg capsule and frees the embryos. It is due to the early develop- ment of these unicellular glands (Fig. 48) that some frog tadpoles hatch in a very immature Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Noble, Gladwyn Kingsley, 1894-1940. New York : McGraw-Hill
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