1881.] Comparative Neurology. 109 
a portion of this ventral chain innervates the anterior buccal and 
and prehensile feet, while the six smaller ganglia of the abdomen 
still correspond to the segments and have more apparent primary 
than secondary significance. In Arachnida, where nerves are 
given off to the enteron from both the cerebral and ventral 
ganglia, an appearance is presented of the vertebrate pneumo- 
gastric projection. 
Recent embryological observations, as set forth by Balfour 
(“ Comparative Embryology,” Vol. 1, 1880) from monographs of 
Kowalevsky, Kleinenberg, Fol, Lankester and others, distinctly 
show that where the nervous system has been made out at all, as 
a rule it proceeds from epiblastic thickening and differentiation. 
The First System arises from intestinal innervation, the ganglion 
of which affords, in Invertebrata, locomotor nervous control. The 
respiratory, digestive, and excretory functions, as in larva of. 
dragon fly and fish Cobitis, being performed, not only by the 
same sets of nerves, but the same organs (vide Darwin’s “ Origin 
of Species,” p. 170). We have seen locomotion to proceed as an’ 
accidental accompaniment of respiration (Branchipus), and the 
sub-cesophageal ganglion innervating the second pair of antennz 
in Nauplius. 
The vaso-motor division of the first system is added when the 
mesoblast appears and the vascular is differentiated. The con- 
centration of the fibers and ganglia of this system in certain areas, 
as the solar plexus, renders any attempt at systematic classifica- 
tion of strands, etc., futile, but by studying the arrangement of 
the sympathetic system backward from the pre-vertebral ganglia, 
the warrant for the scheme I have adopted is more apparent. The 
pre-vertebral are united by longitudinal commissures, precisely | 
as in the ventral chain of ganglia in Arthropoda; often as in the 
cervical region these ganglia coalesce to form larger nerve cen- 
ters, precisely as in cephalo-thoracic formation from metamera, or 
as in the leech; one ganglion may in the adult represent three of 
the embryonic mimestal ganglia. 
No matter how exalted the function or position pertaining toa 
ganglion iz any system, it does not lose its identity as a simple 
center from which afferent and efferent fibers proceed. The pra- 
vertebral chain presides directly as centers over the immediate 
vascular area with which it lies in contact, with its more or less 
obscure peripheral projections, while the commissural system 
