402 MR. NEWPORT ON THE NERVOUS SYSTEM OF THE SPHINX LIGUSTRI. 



In the larva and pupa of the Sphinx, we have seen that these transverse nerves 

 divide and distribute their branches anterior to every ganglion. In the thoracic seg- 

 ments, some of their branches [Plate XIII. fig. 2. (e, h)'] unite with nerves which are 

 already formed by two roots (/, i), one from the cords and the other from a ganglion, 

 and which are destined for the future wings. In the abdomen, after giving some very 

 small filaments to the nerves from the gangliated cords, they are distributed to the 

 muscles of the segments, in addition to the nerves derived from the gangliated cords, 

 and which, there is reason to believe, are compound nerves, and communicate both 

 sensation and motion. I am therefore inclined to regard the transverse as super- 

 added nerves, analogous to the respiratory nerves of the higher animals. In my 

 former paper upon the Sphinx in its larva state, these nerves were believed to be 

 arranged in distinct series, originating separately from the posterior part of each gan- 

 glion. Subsequent examinations have convinced me that the whole form one conti- 

 nuous system [Plate XVI. fig. 35. (c)], and do not originate separately by single tracts 

 from the ganglia, but, as suspected and suggested to me by Professor Grant, 

 pass over the ganglia (h), and are continued along the median line between the 

 cords {/c) until they divide (c, c), to be distributed to the tracheae and muscles. 

 They are formed of three series of fibres, two of which are closely approximated, so 

 as to look like a single tract [Plate XVI. fig. 35. (k)']. This comes down between the 

 cords until it arrives just before a ganglion (A), where it divides nearly at right angles, 

 and unites with the third series, which runs transversely across the body of the 

 insect. A filament from each division (A, h) passes over the outer margin of the upper 

 surface of the ganglion ; then, converging again to the middle line, meets with its 

 fellow from the opposite side : and these two filaments unite, and form one tract, after 

 each filament has received a few fibres (j, i) from the upper or motor surface of the 

 cords. The fibres thus united pass along the groove formed between the cords until 

 they arrive at the next ganglion, where they divide, and distribute again as before. 

 Each transverse series, besides the filament which passes over the ganglion, gives 

 also a filament to the great or moto-sensitive nerve (g, f), which comes from the 

 gangliated cords, and is distributed to the different parts of the segment. The ter- 

 minal pair of nerves of this series is always distributed to the rectum, near its termi- 

 nation, in addition to the last pair of compound nerves from the last great gan- 

 glion. 



I have found these nerves taking nearly the same origin and course in the abdomen 

 of the large green Grasshopper {Gryllus viridissimus, Linn.). After the united fila- 

 ments in this insect have passed along the median line, or groove, between the cords, 

 [Plate XVI. fig. 39.] and arrived above a ganglion, they gradually diverge at an acute 

 angle, and not abruptly as in the larva of the Sphinx. Each division gives a filament 

 to a small nerve, which runs to the diagonal muscles of the segment (c), and which 

 does not originate from the ganglion, but from the upper surface of the cord, or motor 

 tract, which is passing over it, and is probably a motor nerve. The filaments then 



