NERVOUS SYSTEM. 191 



passes through the simplest grades of that system presented 

 by the lowest fishes. The larva of the insect, like the red- 

 blooded worm, is almost a simple cylinder, soft, flexible, 

 smooth, and equal throughout, and the nervous columns 

 then manifest the same equal development from one extre- 

 tremity of the body to the other. The most helminthoid 

 adult form of the whole body presented by the entomoid 

 classes is that of the long equally developed myriapods, and 

 the simplicity of their outward form is accompanied with a 

 corresponding inferiority in the type of their nervous system, 

 and of all their internal organs. Their nervous system is 

 nearly that of the annelida and the larva ; but as their con- 

 solidated segments develop stronger muscular members to 

 support them on the land, their nervous columns and gan- 

 glia are encreased in size, to afford additional nerves to those 

 enlarged extremities. On looking through the abdominal 

 nervous columns of the scolopendra, we can distinctly per- 

 ceive, notwithstanding the transverse approximation of all 

 the parts, a distinct transparent line marking the original sepa- 

 ration of most of the united ganglia. The globular cineritious 

 particles, composing the ganglia, appear often united to form 

 a round isolated mass in the centre of the ganglia, and the 

 same opaque particles, when coagulated, are seen to occupy, 

 in an interrupted manner, the interior of the sensitive 

 columns. The motor columns I have found here of great 

 size, as those shown by Treviranus and by Muller in the 

 equally muscular body of the scorpion. The ganglia, like 

 the segments, are nearly equally developed, and equidistant 

 from one extremity of the chord to the other, excepting the 

 first pair or supra-cesophageal, which give nerves to the long 

 antennae and to the large eyes, and the remarkably small round 

 terminal ganglion below the anus. The intermediate trans- 

 verse motor nerves, pointed out as respiratory nerves by Lyonet 

 in the columns of insects, and by Morren in the annelides, do 

 not here come off, as they do in the earth-worm, midway be- 

 tween the ganglia, but very close behind the ganglionic nerves. 

 Four great nervous trunks originate from the columns on each 

 side at each ganglion, and the second anterior of these 

 branches, which is the largest, proceeds to the muscles of the 

 legs, where I have traced it as far as the tarsal joint. Only 

 two branches on each side proceed from the ganglionic space 



