62 THE ORIGIN OF VERTEBRATES 
The supra-infundibular portion of the brain in vertebrates 
corresponds clearly to the supra-cesophageal portion of the inverte- 
brate brain in so far that in both cases here is the seat of the will. 
Voluntary action is as impossible to the arthropod deprived of its 
supra-cesophageal ganglia as to the vertebrate deprived of its cere- 
brum. It corresponds, also, in that from it arise the nerves of sight 
and smell and no other nerves; this is also the case with the supra- 
cesophageal ganglia, for from a portion of these ganglia arise the nerves 
to the eyes and the nerves to the first antenne, of which the latter 
are olfactory in function. Thus, in the accompanying figure, taken 
from Bellonci, it is seen that the supra-cesophageal ganglia consist 
Sup. Segment Ant I 
-Mid. Segment 
Ant II 
Fic. 27.—TuHE Brain oF Spheroma serratwm. (After BELLONCI.) 
Ant. I. and Ant. II., nerves to ist and 2nd antenne. f.br.r., terminal fibre layer of 
retina; Op. g. I., first optic ganglion; Op. g. II., second optic ganglion; O.n., 
optic nerve-fibres forming an optic chiasma. 
of a superior segment corresponding to the cerebrum, a middle 
segment from which arise the nerves to the lateral eyes and to the 
olfactory antenne, corresponding to the basal ganglia of the brain 
and the optic lobes, and, according to Bellonci, of an inferior segment 
from which arise the nerves to the second pair of antenne. This 
last segment is not supra-cesophageal in position, but is situated on 
the cesophageal commissures. It has been shown by Lankester and 
Brauer in Limulus and the scorpion to be in reality the first ganglion 
of the infra-cesophageal series, and not to belong to the supra- 
cesophageal group. 
Further, in Limulus, in the scorpion-group, and in all the extinct 
