260 
MR. NEWPORT ON THE NERVOUS AND CIRCULATORY SYSTEMS 
junction of the oviducts in Gryllus. It always gives nei-ves to the terminal portion 
of the oviducts, as the preceding ganglion does to the rectum. 
The nervous cord attains its maximum development in the Myriapoda, in the Scolo- 
pendridce and Scutigeridce. Each ganglion now gives off four pairs of nerves, the first 
and third of which are distributed to the muscles, and the second to the feet, while 
the fourth pair, the analogue of the respiratory nerves, lies above the ganglion at its 
posterior margin, but derives from it, as in Geophilus, part of its structure. It is 
closely joined to the side of the superior tract of the cord, from which at first it seems 
to be derived, as I formerly* believed when describing this structure. Its distribu- 
tion to the spiracles in Scolopendra was subsequently shown in the Plates of Mr. 
SwAN-f-, and its analogy to the respiratory nerves of insects has since been pointed 
out by Professor Owen}. The existence of commissural fibres passing through the 
ganglia in Scolopendra, one to each nerve, was also made known by Dr. Carpenter^, 
but the presence of the lateral fibres of the cord has not heretofore been ascertained. 
These lateral fibres exist in the Scolopendra, as already described in the other Myria- 
poda, but are less readily observed than in Polydesmus and Geophilus, in conse- 
quence of the more perfect structure and approximation of all the parts of the cord. 
The ganglia of the anterior segments have approached nearer to each other than in 
Geophilus, more especially the first five, which are separated only by a short portion 
of cord. In Lithobius this approach of the ganglia is carried still further, and in the 
Scutigeridse, in which the first seven ganglia are very closely approximated, it has 
reached its maximum. In these latter instances also, the brain has acquired a greater 
development, the optic nerves and ganglia are enlarged, and the separate organs of 
vision are greatly multiplied. The caudal ganglia are united into a separate larger 
ganglion in Scolopendra, and in Lithobius (Plate XIII. figs. 23 and 24, 17* 18.) form 
an elongated caudal appendage to the last great ganglion of the cord. 
In the * Scorpion idee the nervous system exhibits two opposite conditions in the same 
animal ; that of concentration of structures in the anterior part of the body and ex- 
tension in the posterior, thus reminding us of the pseudo changes which are taking 
place in the anterior segments of the lulus, while growth and elongation of others are 
taking place in the posterior. In the anterior part of the Scorpion the aggregation 
of segments has been carried to its greatest extent, the cephalothorax being formed of 
at least six segments that can be identified, and doubtless of still more ; and not only 
have the ganglia of these segments been collected into one mass, but they have been 
joined by others from the segments of the abdomen, as in perfect insects and Crus- 
tacea. But instead of the nervous cord terminating in the abdomen, as in the most 
perfect of those classes, it is extended backwards and forms a series of ganglia in 
the tail, a condition which marks a close affinity to the macrourous Crustacea and 
* Philosophical Transactions, 1834, Part II., p. 408. 
f Comparative Anatomy of the Nervous System, 1835, Part I., Plate V. fig. 1. 
1 Hunterian Lectures, 1842. § Inaugural Thesis, 1839. 
