All these amphiblastic vertebrates, Petromyzon and Cestracion, Accipenser and Ceratodus, and also the salamanders and batrachia, belong to the old, conservative groups of our stem.
2
The metamorphosis goes farther in a third order of Amphibia, the Batrachia or Anura, than in the salamander.
3
In Batrachia and Reptilia the stomach is in most cases a simple sac, marked off from the oesophagus only by increased calibre.
4
The same applies to the most advanced of the Amphibia, the Batrachia (frogs and toads); some of them have entirely lost the gill-bearing larva form.