the nervous system consists of a distinctly vous system is met with. 
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NERVOUS SYSTEM. (Comparative Anatomy.) 
In the larva of Dyticus marginalis (fig. 347), 
bilobate supra-esophageal ganglion (a), from 
Fig. 347. 
Ventral nervous cord of Dyticus marginalis (larva 
_ state), magnified to about twice the natural size. 
_ 4a, bilobate supra-cesophageal or cerebral gan- 
6, nerves passing to the antenne. c¢, c, 
to the eyes. d, infra-cesophageal 
a the nerves passing to the maxilla, 
, ae andlabium. e¢,¢,e,e, thoracic and ab- 
inal ganglia. /f, f, nervous filaments passing 
to the caudal extremity of the larva. 
7 
which are given off nerves to the antenne, and 
and the eyes (b,c), and of twelve abdominal 
lia, connected by longitudinal cords (c). 
difference in distance of these ganglia is 
ae remarkable, and worthy of mention. The 
it, Or true infra-cesophageal ganglion (d) is 
situated as usual ; atiosens this and the second 
a long space intervenes, and the connecting 
cords are firm and distinct; the spaces between 
the second, third, fourth, and fifth are about 
equal, and not more than one-third the distance 
between the first described ; the remaining seven 
are so closely approximated as to touch each 
other: from the terminal ganglion are given 
off long and minute nervous filaments, which 
may be traced down to the caudal extremity 
of the larva. 
In the Hymenoptera a very great concen- 
= 
611 
tration and increased developement of the ner- 
In the he the 
cerebral ganglion is of a large proportional size; 
from its anterior part are given off two nerves, 
which pass forward to the base of the antenna, 
and have their origin marked by a very distinct 
conical-shaped ganglionic enlargement. In the 
thorax all the ganglia coalesce into one central 
large ganglion, and a smaller one closely at- 
tached to it, giving off lateral nervous filaments ; 
in the abdomen there are five smaller ganglia ; 
they are connected by commissures, as in the 
preceding classes, the double nature of which 
is distinctly seen by a lens: the first abdominal 
ganglion is situated at some distance from the 
thoracic ganglion; the second and third are 
much nearer together, but the fourth and fifth 
are quite closely approximated: from them are 
given off radiating nerves. 
The most highly developed nervous system 
in the Articulata occurs in the Lepidoptera, 
the characters of which we shall next describe. 
In the larva of the Saturnia pavonia minor 
(fig. 348), the nervous system consists of a 
bilobate supra-cesophageal or cerebral ganglion, 
and of twelve sub-cesophageal or abdominal 
ganglia (a), united by longitudinal fissures. 
The cerebral ganglion consists of two closely 
approximated oblong ovate medullary masses, 
giving off nerves supplying the eyes and the 
antenne, and a pair of nerves from its anterior 
and lower parts, which takes a direction for- 
wards, and which meeting inwards and joining, 
forms a ganglion: from the posterior surface 
of this ganglion arises a nerve (the recurrent of 
Lyonnet) which passes backward beneath the 
cerebral ganglion along the csophagus, and 
gives off filaments to itand the stomach.* The 
existence of this nerve, and particularly its si- 
tuation, is of very high importance, according 
to the laws of philosophical anatomy: the 
branching filaments it sends off form nervous 
rings, which are important in being open be- 
low and not above, and in developing a gan- 
glion on the dorsal aspect of the animal; this, 
we shall find presently, leads by strong ana- 
logies to the Vertebrata. The cerebral gan- 
glion is supported or produced by two lateral 
nervous filaments, which, having their origin 
at its posterior part, pass downwards by the 
sides of the esophagus, at the inferior part of 
which they converge, and are connected with 
the first sub-cesophageal ganglion; in this way 
a nervous collar or ring is formed, which en- 
circles the esophagus. This first inferior gan- 
glion (6) is of rather a quadrilateral form ; it 
gives off a pair of nerves to the maxille and 
to the labium (c,d), which have their origin 
within, the termination of the lateral commis- 
sures just described. The second ganglion is 
longitudinally continuous with the first; from 
them are given off lateralnerves. The (supposed ) 
motor and sensitive connecting nervous columns 
are widely separate between the second and third 
ganglia, and between the third and fourth ; 
between all the others they are very closely 
* This nerve is considered by Mr. Newport as 
the analogue of the par vagum. 
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