ON THE ANASPIDACEA, LIVING AND FOSSIL. 545 
and are supplied with a dorsal (G.B.) and ventral (G. D.) 
ganglionic mass on each side. Their fibres form thick trans- 
verse longitudinal bands in the ventral part of the brain, with 
complicated branches passing posteriorly. The autennary 
nerves (Ant. 2) enter the brain laterally and ventrally, and 
are supplied with a very large dorsal ganglionic mass (GG. c.), 
which passes anteriorly underneath the fibres of the optic 
nerves, and a smaller ventral mass (G. H.). The fibres which 
enter the brain from these nerves form a very complicated 
and massive system, occupying the whole of the posterior 
part of the brain. 
The peri-cesophageal commissures (com.) are short, and 
ventrally to the cesophagus they come together in the sub- 
cesophageal ganglion (swb. gn.), which gives off three nerves 
to the mandible and two pairs of maxille. 
(a) Theoretical Considerations. 
If we pick out the more important points in the internal 
anatomy of Anaspides, in order to compare it with the 
other Malacostraca, we perceive that its internal anatomy 
is of*a generalised type resembling in some respects the 
Peracarida and in others the Hucarida, especially the Deca- 
poda. 
The chief Peracaridan features are the elongated, tubular 
heart and the filiform spermatozoa, while the possession of a 
maxillary gland is paralleled by certain Peracarida (Isopoda). 
The alimentary canal, on the other hand, in so far as it is 
not peculiar, recalls that of the Decapoda. The nervous 
system is of an unconcentrated primitive character, with a 
discrete ganglion in each thoracic and abdominal segment. 
Comparing these conclusions with those derived from a con- 
sideration of the external characters, we may observe that 
they are in completeagreement. From the external characters 
of the limbs and of the segmentation we judged that the 
Anaspidacea stood midway between the Peracarida and the 
Hucarida, but on a more generalised and primitive plane, 
