In the Amphibia the brain is of a low type, the most marked advances
on that of the fish being that the anterior commissure is divided into
a dorsal and ventral part, of which the ventral is the true anterior
commissure of higher vertebrates, while the dorsal is a hippocampal
commissure and coincides in its appearance with the presence of a
small mass of cells in the outer layer of the median wall of the
pallium, which is probably the first indication of a hippocampal
cortex or cortex of any kind (Osborn, _Journ. Morph._ vol. ii., 1889,
p. 51).
[Illustration: From _Cat. R.C.S. England_.