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NERVOUS SYSTEM. (Comparative Anatomy.) 
~ 
Seren though by a lens the fissure or 
mark of separation may in some be perceived. 
The abdominal ganglia are of a lengt 
ovoid form; and when viewed couta a 
have a dense opaque white ae 
in particular ba pei eer as it were i 
neurilemma, have a distinctly bilobate ap 
pearance; in others there appears 
nucleus of opaque nervous matter(8&9); from 
each of them are given off three lateral pairs o 
nerves, some of which pass to su 
viscera, while others pass rourd the 
the larva to near the dorsal vessel, thus formir 
a nervous ring, open superiorly, which bein 
repeated in each segment, and the whole ec 
nected by commissures, forms a cont 
Series at once recognised as a column of ori- 
mary nervous rings, the type of the nervous 
system of the articulata; the eleventh 
twelfth ganglia are closely joined to each o 
and from the latter are given off two radi 
pairs of nerves, ing to the caudal e: 
of the larva. ere is also a. minute ner 
(fig. 348, f), which I have traced in this | 
passing ie at the angle of separation between 
the divided longitudinal connecting t th 
second and third, and per Pi and 
abdominal ganglia, and whi midway 
tween these ganglia, divided into a ri 
left transverse filament (g, g), each 
had connexion with the steel nerves 
from the ganglia themselves. Some have ec 
sidered these nerves as sympathetic, ¢ 
as motor, but from their principal b 
going to supply the trachee, I cesider a 
Mr. Newport, that they must be respira 
nerves. ’ 
I have examined the nervous cord in 
larva of Pontia brassica, naan r 
two species of Arctia, and have ¢ 
position of the ganglia, &c. to be the 
as the insect, however, advances towards t 
turity, considerable and important char sat 
place in the nervous system. it 
described and figured them in the Por 
sica,* and Mr. Newport has investiga’ 
with the minutest accuracy in the § 
gustri.+ It appears that during the p upa 
a contraction of the nervous colum st 
lace, the lia (more B} become 
ay third fourth, and fifth) become 
mated ; the distance between the ¢ 
glion and the first sub-ceso 
becomes much less, and the cesophage 
becomes much smaller; this is preparat 
the subsequent | concentration nd ji 
which we find in the perfect insect. — 
this latter phenomenon takes place, th 
just mentioned become consolidated to; 
and the oral nervous ring is scarcely 
tible: this is the case in the perfe 
Mormo maura (fig. 349), where also t 
dominal ganglia are snail (cc), and ¢ : 
the disappearance of two of the thoracie 
are situated at some distance fone 
which are of large size (6 6), and t 
* Entwickelungsgeschichte des § etterli 
+ Phil. Trans. for 1832 and 1834, 4 
