arated
from it, is called the _pyriform lobe_. In the Lacertilia the pineal
eye, if it be an eye, is better developed than in any existing
vertebrate, though even in them there is no evidence of its being used
for sight. Behind the so-called pineal eye and its stalk is the
_epiphysis_ or pineal body, and sometimes there is a dorsal sac
between them (see fig. 18).[1] The middle or soft commissure appears
in certain reptiles (_Crocodilia_ and _Chelonia_), as does also the
_corpus mammillare_ (Edinger, Senckenberg, _Naturf. Gesell._ Bd. xix.,
1896, and Bd. xxii., 1899; Haller, _Morph. Jahrb._ Bd. xxviii., 1900,
p. 252). Among the birds there is great unity of type, the cerebellum
is large and, by its forward projection, presses the optic lobes down
toward the ventro-lateral part of the brain. The cerebral hemispheres
are also large, owing chiefly to the great size of the _corpora
striata_, which already show a differentiation into caudate nucleus,
putamen and globus pallidus. The pallium is reptilian in character,
though its cortical area is more extensive. The geniculate bodies are
very large (Bumm, _Zeits. wiss. Zool._ Bd. xxxviii., 1883, p. 430;
Brandis, _Arch. mikr. Anat._ Bd. xli., 1893, p. 623, and xliii., 1894,
p. 96, and xliv., 1895, p. 534; Boyce and Warrington, _Phil. Trans._
vol. cxci., 1899, p. 293).

Among the Mammalia the Monotremata have a cerebellum which shows, in
addition to the central lobe of the lower vertebrates, a flocculus on
each side, and the two halves of the cerebellum are united by a
ventral commissure, the _pons varolii_. The pallium is reptilian in
its arrangement, but that part of it which Elliot Smith has named the
neopallium is very large, both in the Ornithorynchus and Echidna, a
fact very difficult to account for. In the latter animal the cortical
area is so extensive as to be thrown into many and deep sulci, and yet
the Echidna is one of the lowliest of mammals in other respects. A
well-marked rhinal fissure separates the pyriform lobe from the
neopallium, while, on the mesial surface, the hippocampal fissure
separates the neopallium from the hippocampal area. Just below the
hippocampal fissure a specially coloured tract indicates the first
appearance of the fascia dentata (see fig. 20). The anterior
commissure is divided, as in reptiles, into dorsal and ventral parts,
of which the latter is the larger (fig. 20, _Co