i53 



HARDWICKE'S SCIENCE-GOSSIP. 



the 2nd segment. Upon either side of this dorsal 

 aorta processes were present ; they occur in pairs, 

 one pair in the anterior and one in the posterior of 

 each segment. They contain sometimes a brown and 

 sometimes a green material, apparently similar to the 

 respiratory tissue which is composed of brown cells in 

 the abdominal segments, but appears green in those of 

 the thorax. (Fig. 62.) 



The Respiratory System. — Branching cellular tissue 

 is apparent in the 4th, 5th, 6th, 7th, 8th, 9th, and 

 10th segments. In older specimens it is present, 

 though less abundant, in the 1st, 2nd and 3rd, and 

 scattered sparely in the nth. The branching is 

 intricate, but there is no connection between the 

 branches in the separate segments. Upon each side 

 of the segments in which the branches occur, may be 

 noticed three or four small oval impressions clustered 

 together, they occupy the position of stigmata. 

 (Query. Is the integument thinner in these parts ?) 

 In my earlier observations I thought I could detect a 

 long transparent vessel upon each side, starting from 

 the neighbourhood of the nth segment. They 

 appeared shining and colourless through the red 



wifa \ 



IT 



Fig. 66. — The Nymph. 



integument, and traversed the region of the body 

 where the respiratory tissue was most abundant. I 

 traced them forward to the 3rd segment. I have 

 since detected portions "of transparent vessels that 

 apparently start from, or enter into the processes of 

 the nth segment and appear intimately connected 

 with the respiratory tissues in the nth segment. (I 

 am unable to thoroughly satisfy myself concerning 

 these last appearances, as later observation shows the 

 two lateral lines disconnected between each segment.) 

 The walls of the processes are extremely thin. 



In very young larvae, a loose cellular tissue is visible, 

 in the interspaces of the viscera. This structure takes 

 the place of the branching system and gradually 

 developes into it. In old larvse, branching, vascular 

 trachea; are apparent in the 1st segment upon each 

 side. In the nymph they appear as external tracheae. 

 (Fig. 63.) 



The Nervous System. — The supra-cesophageal 

 ganglion occurs in the 1st segment ; looking down 

 upon the larva, it appears as a bilobed mass. (In 

 very young larva;, this ganglion is comparatively 

 larger — as are all the other — and lies half within the 



head and half within the 1st segment ; in this stage I 

 was able to trace nerve threads to each of the eyes.) 

 The supra-cesophageal ganglion is united on each side 

 to a smaller ganglion, beneath the gullet, the infra- 

 cesophageal ganglion by a broad commissural cord. 

 There is another small ganglion lying in the 1st 

 segment, immediately following the infra-cesophageal, 

 and they are two other similar ganglia in the 2nd 

 segment, one anterior and one posterior ; while similar 

 ganglia occur anteriorly in the 3rd, 5th, 6th, 7th, 

 8th, 9th, and two in the 10th segment. 



In the very young larva 3 , there is a ganglion in the 

 4th, and one only in the 2nd, and each ganglion at 

 that time shows clearly its double origin. The- 



a- 



\ I v I 



Fig. 67.— [a) head of male ; (/>) head of female. 



ganglia are united by double commissural cords- 

 (Fig. 64.) 



The Muscular System. — The muscles appear as ; 

 narrow striated bands. Those from the mandibles and 

 other mouth parts are inserted in the posterior walls 

 of the head. The muscles from the head are inserted 

 at the junction between the 1st and 2nd segments, and 

 those of the body appear to be attached and inserted 

 to the anterior of each segment. The fore-limbs are 

 furnished with retractor and extensor muscles ; the 

 former are attached to the anterior inner walls of the 

 rounded hook-bearing processes and inserted in the 

 dorsal posterior walls of the 1st segment. By their con- 

 traction they draw in the process as you might draw 

 in a tape, the lines of books lying forward the while. 

 The extensor muscles are attached to the posterior 

 walls of the limb and inserted in the posterior dorsal 



