Amphibia. 189 



ing at the inner end of the oviduct and as they pass along 

 the duct are coated with a layer of gelatinous material 

 which swells up after the eggs are laid, so that each egg 

 appears as a small, spherical, glassy body, with its upper 

 part of a dark color, and surrounded by a spherical mass of 

 clear, jellylike substance. In a few weeks the form of the 

 body begins to appear. The tail begins to vibrate, the sur- 

 rounding mucus breaks up and the tadpole emerges with gills 

 very much like a tiny fish. For a short time there is no 

 mouth opening, and the little tadpole attaches itself to water- 

 weeds by suckers near the place where the mouth is to 



FIG. 119. DEVELOPMENT OF A TOAD. 



From Packard's Zoology. 



appear. After the mouth, with horny lips and jaws, is 

 developed, the tadpole feeds greedily on waterweeds and 

 grows rapidly. The external gills disappear and are replaced 

 by internal gills, which are concealed by a fold of skin which 

 incloses a gill chamber. There is an opening on the left 

 side of the body for the water to escape. The limbs de- 

 velop as little projections, like buds, on the sides of the 

 body ; but the anterior limbs are for a long time concealed 

 by the gill chamber and therefore appear to develop later 

 than the hinder pair. At first the tadpole swims, fishlike, 

 wholly by means of the tail, and it continues to do so long 

 after the limbs appear. It holds the limbs close by the side 



