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Amphibians
This group includes frogs, toads, salamanders
etc. They resemble the fishes especially the lung
fishes. The modern amphibians are essentially
fishes in their early life when they are tadpoles;
later legs sprout the tail becomes absorbed and lungs
take the place of gills. Judging from these facts, we
may assume that fish like ancestors from the
development of lungs became fitted for life on
land and that from these the amphibians of
today have been derived.
The most interesting of our amphibians in
Colorado, is the tiger salamander. In the east this
species drops its gills in early live and assumes the
adult form, but in the cold waters of Colorado and
neighboring states it may never become adult, but
always retain its gills. The peculiar thing in their life
history is that these immature salamanders breed
in their immature state. They are locally known by
the name of Axolotl and we commonlly call water
dogs, mud puppies etc.