ON THE ANASPIDACEA, LIVING AND FOSSIL. 543 
fibres, and in the ganglion they form thick bundles of 
transverse commissures which anastomose in the thick fibrous 
region in the ventral middle line. A ganglionic mass is 
applied to the dorsal surface of this nerve (G.1) and also to 
the ventral (G.2). The two nerves to the muscles are seen 
issuing more posteriorly from the ganglion; their fibres also 
lie ventral to the commissural longitudinal fibres. A 
TExT-FIG. 45. 
Reconstruction of a thoracic ganglion of Anaspides tas- 
manixw. com. Longitudinal commissures of cord. WN. 1. 
Nerve to appendage. N.2. Nerve to ventral muscles. N. 3. 
Nerve to oblique muscles. G. 1. Dorsal ganglionic mass. 
.2and 3. Ventral ganglionic masses. 
ganglionic mass (G@. 3) is situated only on the ventral surface 
at the exit of these nerves. 
The brain or supra-cesophageal ganglion gives issue to 
three nerves, the optic (opt.), antennulary (Ant. 1), and 
antennary (dnt. 2) nerves. 
The optic nerves spring from the dorsal surface of the 
brain, being the only nerves with this position of origin. 
