CENTRAL NERVOUS SYSTEM IN VERTEBRATE ANIMALS. 
957 
r. c. Restiform column. 
s. g.c. Substantia gelatinosa centralis. 
s.r. Fourth ventricle or sinus rhomboidalis. 
s. v. Saccus vasculosus. 
t. Tectum lobi optici. 
t.c. Transverse commissure of the cerebrum. 
t.c.t. Transverse commissure of the tectum. 
t.c.v. Transverse commissure at the root of the vagus. 
t.f. Trigonuin fissum. 
t.i. Tuberculum impar. 
t.l. Torus longitudinalis. 
t.s. Torus semicircularis. 
t. v. Tuberosity of the vagus. 
u. c. 5. Upper column of the trifacial. 
v. c. Yalvula cerebelli. 
v.g. These appear to correspond to the vincula gelatinosa centralia of 
Fhitsch, l.c., p. 44. 
v.h. Ventricle of the hypoarium. 
v.h.g. Ventral horn of grey matter in the spinal cord. 
v.l.c. Ventral longitudinal column. 
v.op.l. Ventricle of the optic lobe. 
v.r. Ventral root of the spinal nerves. 
v.t.c. Ventral transverse commissure in the medulla oblongata and the 
spinal cord. 
v.th. Third ventricle or thalamencephalon. 
PLATE 59. 
Fig. 1. Longitudinal and vertical (sagittal of authors) section through the brain of a 
young Hyperopisus dorsalis , close to the central line. X diameters 
about. The dorsal part of the lateral wing is left in outline. The anterior 
wing has become slightly bent upward; it ought to be parallel to the long 
axis of the brain. 
** Show the line of section taken in fig. 3. 
Fig. 2. Transverse section through the anterior part of the optic tract and the tecta 
lobi optici of another specimen of the same species. The lateral and 
dorsal wings of the valvula cerebelli have been left in outline. X 15^ 
diameters nearly. 
Fig. 3. Transverse section through the centre of the tectum lobi optici at a point 
slightly behind the last, taken from the same specimen. X 15^ diameters 
nearly. 
