'line ('ATi:itl'II>LArv: IXTEIIXAL ORGANS. 23 



iilinientarv canal and (.'xpands Into a pair of li^bcs, to near the ti[) of tlic 

 abdomen. 



V^iewed fi'oni above, tlic cej)lialic ganglia consist of a pair of nearly glo- 

 bular or 8ul)pyriforni lobes, closely joined by their inner edges, or at least in 

 juxtaposition ; they are situated in the very middle of the head, just above 

 the beginning of the alimentary canal, and on a level, above, with the top 

 of the frontal triangle. From the lower anterior outer angle of each lobe, 

 the optic nerve, large at base, but gradually tapering beyond, ])asses down- 

 ward, forward, and outward, in a straight course toward the ocelli ; as it 

 reaches them it expands into a broad field c()m])rising the ocelli, — l)la(k 

 conical masses, their apices })lunged in the nervous tissue forming the field. 

 Just behind the origin of the optic nerve another inde})endent nerve arises, 

 extending to the ii[)per ])ortion of the tendinous cord which terminates the 

 great muscular mass of the head and moves the mandibles. A little further 

 removed from the optic nerve, and on the lower anterior edge of each lo])e, 

 a little witiiiu the middle, another slender nerve arises, which runs in a 

 straight course to the base of the antennae. 



From the lower outer edge of each cephalic lobe a nervous cord passes 

 downward and a little backward, the two embracing the oesophagus, and 

 then converges until they unite in the suboesopliageal ganglion, a horizontal 

 lenticular disk, situated at the base of the head just above its hinder edge ; 

 just beneath the oesophagus these embracing cords are united by a cross 

 thread ; this suboesopliageal ganglion throws out lateral nerves, directed 

 forward and outward, and is strapped in its place by transverse muscles, 

 one just in front and another just behind it, which originate together on 

 the floor of the body ; and the hinder of which is strengthened on each side 

 by a secondary muscle, which runs liackward beside the cord for a short dis- 

 tance, divaricating slightly. 



The ganglia of the body-segments, which are similar in general character 

 to the suboesopliageal ganglion, are situated in or near, generally a little in 

 advance of, the middle of each segment, as far as the seventh abdominal 

 segment, where there is a pair, in close proximity, one behind the other, 

 and Avith these the nervous cord terminates. All the ganglionic disks are 

 connected by a pair of ribbons, generally lying in such close proximity as 

 to appear to be single and straight, but anteriorly they are separated some- 

 what widely. 



In leaving the suboesophageal ganglion, the nervous ribbons run nearly 

 })arallel, or with only a slight outward curve, to the first Ijody-ganglion. 

 Starting again close together at the middle of the posterior border of the 

 first ganglion they diverge in straight lines, but very gradually, until they 

 are nearly twice as far apart as the width of the first ganglion (which is 

 often twice as far removed from the second as from the suboesopliag(>al 

 ganglion), and then converge more rapidly and enter the second ganglion 



