AMPHIBIANS 



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capable of a large amount of motion; it differs essentially from that of the higher 

 Vertebrates in that it is affixed to the inner side of the front of the lower jaw, with 

 its tip pointing down the throat. 



All Amphibians lay eggs, which are generally although not inva- 

 riably deposited in fresh water, and fertilized as they are extruded 

 from the female. As a rule, these eggs,, which much resemble those of fish, are 

 small, very numerous, and connected by mucilage, forming either a string or 

 a jelly-like mass in which the dark yolks are very conspicuous. Some of the 

 tree frogs, however, lay large eggs, within which the larvae undergo the whole of 

 such transformation as takes place; and in one genus, instead of the usual gills, a, 

 temporary breathing organ is developed on the tail. A land frog in the Solomon 

 islands also lays large eggs, like small marbles, which are deposited in the crevices 



DEVELOPMENT OF THE FROG. 



1. Eggs when first laid; 2. Eggs at a later stage; 3. Egg containing embryo; 4. Newly-hatched larvse; 

 5, 6. Larvae with external gills; 7-12. Later stages in the development of larvae. 



of the rocks, and from which emerge fully-developed frogs. The eggs, with certain 

 exceptions, are deposited in water, where they are hatched by the heat of the sun; 

 and it appears that the dark color of the yolk is for the purpose of absorbing as 

 much solar heat as possible. Such eggs as are laid during the late spring and 

 summer are less darkly colored, and have thinner coats, than those deposited in the 

 early part of the spring; and while the former are placed on the ground at the 

 bottom of the water, the latter float on the surface; the reason of this difference 

 being that in the early part of the year the lower strata of water are too cold to 

 admit of the development of the ova. In ordinary cases, when the larva has 

 reached a certain stage, it bursts the investing membranes of the egg, and comes 

 into the world adapted for an aquatic life, and always possessing a long compressed 

 tail composed of zigzag-shaped masses of muscles, similar to those of fishes. The 



