IIE RAGE, TONGS Ole PS EUBS) 
So with the gills, however long they may last. It is now 
believed that they are not, so to speak, retentions of the 
fish gills, but gills peculiar to the larva of the amphibian. 
To take a third feature in the anatomy of tadpoles : 
they are most of them furnished with an elaborate 
series of horny teeth within the mouth ; these “ teeth ” 
are not later developed into the proper teeth of the frog, 
nor do they persist when the tadpole leaves the water 
and begins to croak. They are purely and simply larval 
organs. Ina few amphibians this nearly universal dis- 
tinction between the two groups under consideration 
is not to be met with. But if in a given tree-frog the 
young frog is hatched at once from the egg as a frog, 
without passing through the preliminary tadpole and 
tree living stage, it does not follow that that tree-frog 
must be removed from all other tree-frogs almost 
exactly like it, and placed with the reptilia. In zoo- 
logical classification we constantly come across examples 
of animals most clearly affined to other animals and yet 
lacking one or more of their important characteristics. 
So much then for the difference between amphibia 
and reptiles. There is no doubt that the amphibia 
stand on a lower level than the reptiles, and that there 
are distinct points of likeness to the fishes, some of which 
have already been touched upon. In addition to those, 
is the rather important fact that among the amphibia, 
at least in the larval stages, is a representative of the 
so-called “lateral line”’ of fishes. In any fish it can 
be easily noted that a marked line runs along the sides 
of the body often dividing the darker colour of the back 
from the more silvery hues of the belly. This line is 
formed of a series of sense organs of the nature of touch. 
{n spite of these various points of likeness between the 
fishes and amphibians, there are profound differences. 
The most profound is of course that all amphibians 
agree with the animals lying higher than themselves 
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