A history of British reptiles / By Thomas Bell.

  • Thomas Bell
Date:
1849
Catalogue details

Licence: Public Domain Mark

Credit: A history of British reptiles / By Thomas Bell. Source: Wellcome Collection.

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    cavity, and concealed by a little operculum of the integu- ment. The eyes are now perfectly formed. The holders have become much diminished in size; the mouth has acquired moveable lips, and has changed its position from the in- ferior part of the head to near the extremity, and the little creature which has hitherto derived its sustenance either from its own resources or by absorption, now seeks its food amid softened and decomposing vegetable matter. The caudal web (fig. 8) has, therefore, become considerably de- veloped, and serves for very rapid as well as varied loco- motion. The colour of the body, too, has undergone a considerable change, having become of a soft olive green, the abdomen being dotted with golden yellow. The Tadpole now undergoes but little change in its ex- ternal form for a considerable time, but increases rapidly in bulk, and by and by a little tubercle appears on each side of the vent, which is the rudiment of the posterior extre- mity ; this soon acquires somewhat the form of the perfect limb, the toes budding, as it were, at the extremity, but it still continues very short, even in proportion to the dimi- nutive size of the animal (fig. 10). Meanwhile the anterior extremities are also budding forth in the same manner, and gradually assume their distinct and final form. As the hinder extremities become developed, the tail, the former organ of progression, is removed by absorption, not thrown ofi*, as has been erroneously stated. This is a gra- dual process, the absorption beginning at the apex, and pro- gressing onw'ards to the base, until the whole is removed ; so that the posterior part of the body becomes rounded, and the cloacal opening, instead of being placed beneath, is directed somewhat upwards. Fig. 11 exhibits the young Frog with a small portion of the tail still remaining unabsorbed.
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