MR. NEWPORT ON THE NERVOUS SYSTEM OF THE SPHINX LIGUSTRI. 397 



gradually assume a more lineal direction, and diverging from the axis of the eye, the 

 whole nerve, when completed, forms a series of flattened pear-shaped cones, one within 

 the other, the apices of which constitute the base or origin of the nerve next the cerebral 

 ganglia. The eye of the Sphinx, when perfect, being convex, the outer or first com- 

 pleted series of fibres is the shortest, while each succeeding series is longer and less 

 earlier perfected in proportion to its distance from the circumference, so that the 

 central fibres are the longest and last developed. Thus the same law which regulates 

 the development of the osseous structure, as shown by Dutrochet in the vertebrae 

 of the frog, regulates that of the ganglia and nerves. The common covering of the 

 optic nerve is formed of an extension of the theca which covers the cerebral and 

 suboesophageal ganglia and nerves, and through which the ramifications of tracheal 

 vessels penetrate in considerable abundance. In the optic nerve, in particular, they 

 are very numerous ; and I have never yet been able to detect their terminations, or 

 to discover any other description of vessels in the nerves or ganglia, although there 

 is scarcely a doubt that others do really exist. 



It is difficult to observe the radii of the optic nerve in the Sphinx, owing to the size 

 and opacity of the part ; but the sacculi of nervous matter are beautifully seen in the 

 nerve of the eye of Papilio Urticce, Linn., at about forty-eight hours after changing to 

 the pupa state. It is necessary to remove the nerve with the cerebral ganglia from 

 the head of the insect, and view it with a good lens by intense transmitted sun-light 

 [PlateXV. fig. 31.]. 



c. Nerves of the Mouth and its parts. — These originate from the first suboesophageal 

 ganglion, and from the crura which unite it with the cerebral ganglia. In the larva 

 they supply the mandibles, palpi, and pharyngeal region; and in the perfect insect 

 the two halves of the flexible and delicate proboscis, the structure and muscles of 

 which, in order to show the arrangement of its nerves, I must briefly notice. This 

 organ in the perfect Lepidoptera has recently been described by Mr. Newman * in his 

 Letters on the External Anatomy of Insects, and is shown to be analogous to the 

 maxillae, or lesser jaws. It is situated, in the larva, beneath the strong mandibles, 

 which in the perfect state are obsolete, and exist only as very minute parts on each 

 side its connexion with the head. It is an elongated, tapering, flexible organ, com- 

 posed of two symmetrical halves, placed laterally together, convex on their external, 

 and concave on their internal surface [Plate XIV. fig. 15. a, ^.], and by their approxi- 

 mation forming a tube to the mouth, which is nearly of the same size through its 

 whole length, excepting at the tip, where it is a little smaller. Each half is slightly 

 ciliated externally, and along the whole anterior margin of its concave surface is fur- 

 nished with a row of minute hooks, and near the tip, along its anterior and external 

 surface, with a number of little elongated papillae, which, probably, are organs of 

 taste. In a state of rest, the proboscis is rolled up spirally between the labial palpi ; 



* Entomological Magazine, Part VI., January 1834. 

 MDCCCXXXIV. 3 F 



