OF INSECTS. 
177 
in the abdomen, the nerves descend in long threads 
from the thoracic knots. 
Mr. Newport, following up a discovery of Lyonnet's, 
has lately made us acquainted with a delicate system 
of nervous branches appropriated to the respiratory 
organs, which lies above the ventral chain, following 
it without interruption through its whole extent. It 
consists of a very slender thread placed on the median 
line of the longitudinal cords, but not easily distin- 
guishable except where these are separated ; it then 
seems to spring from the inferior angle of each gan- 
glion, although, in reality, it passes above it. At 
a little distance from that point it divides into two 
branches, which extend laterally in opposite directions. 
No knotty expansion is visible in caterpillars, but in 
Carabus and Gryllus there is a distinct one at each 
dichotomous division of the filet, especially in the 
thorax, where these nerves are most highly developed. 
As the changes which they undergo in the course of 
metamorphoses do not correspond to those that take 
place in the ventral chain, which always tends, with 
every successive development, to a higher state of 
concentration, Mr. Newport regards these nerves as 
forming a separate system, and he has named them 
the auxiliary, transverse, or respiratory nerves.* 
The preceding descriptions will be better under- 
stood by the illustrative figures on Plate IV. Fig. 1 
represents the nervous tree of the common cockchafer, 
which may be regarded as the type of that division 
* Philosophical Transactions for 1032-4. 
M 
