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



and at its base, in some Lepidoptera, there are small maxillary palpi. It is con- 

 nected above with the triangular arch or palate, the epipharynx*, which forms the 

 roof of the mouth, and below with the hypopharynx, or analogue of the tongue, which 

 forms the floor of the mouth, and conducts to the oesophagus. The mouth is only a 

 dilated cavity between the proboscis and commencement of the oesophagus [fig. 15. c.]. 

 Each half of the proboscis is furnished with two kinds of muscles, longitudinal and 

 transverse, acting as flexors and extensors. The transverse muscles consist of many 

 short semicircular fibres, which encircle the exterior of the proboscis [fig. 16. (c. c),] 

 and are attached along the margin of the inner or grooved surface of the organ, which 

 by their contraction they tend to elongate. These muscles are exceedingly small and 

 numerous, and amount to at least one thousand in each half of the organ. They are 

 assisted in their action as extensors by one of the longitudinal muscles {h), which 

 arises within the anterior of the cranium, and is attached by a multitude of fibres, in- 

 serted at very acute angles along the anterior margin of the groove. This muscle, in 

 conjunction with the circular ones, acts as a powerful elongator of the proboscis at 

 the instant of taking food. The other two longitudinal muscles are flexors {a, a). 

 One of these, the direct antagonist of the first, arises from the under surface of the 

 head, and is inserted along the inferior margin of the groove, and assists in rolling 

 up the organ. The other, a more powerful flexor than the last, is the largest of the 

 three longitudinal muscles. It arises from the lateral and under surface of the head, 

 and is attached to the inner surface of the exterior, or most convex part of the organ, 

 by many long fibres inserted at very acute angles into a slight tendinous ridge, so as 

 to compose one large penniform muscle [fig. 16. («).]. Each half of the proboscis is 

 also supplied with one large and one small tracheal vessel [Plate XV. fig. 19. (/. //)], 

 derived from those of the head (g). These extend from one end of the organ to the 

 other, giving off^ numerous branches, and gradually decrease in size, and distribute 

 longer, and a greater number of branches the nearer they approach the end of the 

 organ, so that, as in other parts of the body, they are lost in the surrounding structures. 

 The nerves of the proboscis extend along the course of the tracheal vessels (a, h, c, d, e). 

 In the larva we have seen that the nerves to the mandibles come from the anterior of 

 the subcesophageal ganglion [Plate XV. fig. 34. (1./).] ; and the same is the case with 

 the nerves of the proboscis in the perfect insect [Plate XIV. fig. 10. {a. 1).]. The nerves 

 of this organ in the larva are of inferior size ; in the perfect insect they are largely 

 developed. They originate on each side the subcesophageal ganglion as single trunks, 

 one to each half of the organ. Immediately the nerve has entered the hinge anterior to 

 the mouth, it is divided into four branches. One of these {b) passes backwards, appa- 

 rently to the palpus, and others forwards into the organ. The innermost branch (c) 

 is small, and gives off" very minute filaments. It passes in a direct line immediately 

 beneath the grooved or mucous surface between it and the large trachea, and does 



' * Newman. 



