Fig. 17. — Developuieut of the frog. 1, eggs when first laid ; 2, eggs 

 at a later stage ; 3, egg containing embryo ; 4, newly hatched 

 larvae or tadpoles; 5, 5, 5, tadpoles with external gills; 6 to 11, 

 later stages in the development of the tadpole ; 12, perfect frog. 



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