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



(g, c); and the connexions of these with the cerebral ganglia {b, a.), the antennae 

 (d. a), the manducatory nerves (d), and the transverse or involuntary series (c). At 

 a later period this becomes almost impracticable, owing to the completion of struc- 

 tures among which the nerves of connexion are distributed. Indeed, after this period 

 it becomes more difficult to trace any of the nerves in the anterior part of the body, 

 the whole insect being rapidly approaching to its perfect condition. 



By the first week in June the processes which form the division between the thorax 

 and abdomen, and the attachment for the great muscles of the body, are completed. 

 The muscles themselves have acquired a consistency and strength which they have 

 not before possessed ; the exterior of the perfect insect is nearly completed beneath 

 the pupa-case ; the pink-coloured deposit is extended in the form of little scales over 

 the upper and anterior part of each abdominal segment, and a similar deposit in the 

 form of a black band, but with fewer traces of scales, exists also upon the posterior 

 part of each segment ; while the whole under surface of the body is covered with a 

 thick, semi-opake, greyish-coloured fluid, in which traces of minute scales are very 

 evident. The antennee, the legs, and the wings, folded in their envelopes beneath the 

 thorax and first segments of the abdomen, are still exceedingly delicate and vascular, 

 and are covered also with scales. The nervous system has now arrived at the last 

 stage of development. During the period between this and the previous stage the 

 optic nerve has been greatly enlarged and extended, and the dark-coloured patch has 

 been expanded over its extremity, and seems now to constitute the choroid membrane. 

 But the eye is not yet completed, although the optic nerve seems very nearly to have 

 arrived at its maximum of development. The exterior portion of the organ, next the 

 pupa-case, the cornea, is still of a transparent gelatinous substance, and the lenses ap- 

 pear to be the last parts of the eye which are completed. The cerebral ganglia are 

 now extended transversely, and form, with the first sub oesophageal ganglion, and the 

 enlarged crura which connect them, one continuous mass around the oesophagus and 

 anterior part of the dorsal vessel [Plate XIII. fig. 6. a.]. The second ganglion has 

 entirely shifted its position, and receded towards the middle of the thorax, and has 

 coalesced with the third, which has entirely disappeared, and seems to have joined in 

 part with both the second and fourth, and the intervening cords. This aggregation of 

 ganglia and cords [Plate XIII. and XIV. figg. 6. and 8, (2, 3, 4, 5.)] is situated in the 

 middle of the thorax, and supplies all the muscles in that part of the body. The longi- 

 tudinal cords are continued from the hinder part of the fifth ganglion, and just before 

 leaving the thorax to enter the abdomen they give off the nerves which formerly 

 belonged to the sixth ganglion [fig. 6. (6)], which is now entirely obliterated. The 

 cords then descend into the abdomen, and immediately give oflf the nerves that be- 

 longed to the seventh ganglion, [fig. 6, 7.], which, with part of the cord that existed 

 between the sixth and seventh ganglia, is also obliterated. The cords are then con- 

 tinued in a direct line along the abdomen, the eighth, ninth, tenth, and eleventh gan- 

 glia being situated as in the previous stages. 



