MR. NEWPORT ON THE NERVOUS SYSTEM OF THE SPHINX LIGUSTRI. 417 



remarked that the greatest rapidity and extent of change in the Sphinx occurs during 

 a short period immediately subsequent to its becoming a pupa. This is in perfect 

 accordance with the changes in the Butterfly. 



b. The means by which the development of the two insects take place are similar. 

 They depend chiefly upon a shortening of the longitudinal and diagonal muscles of the 

 body, when the parts of the future insect which have been forming in the larva have 

 aiTived at the greatest development they are capable of in that condition, and, as in 

 the foetus of vertebrated animals, at the completion of the full term of utero-gestation, 

 induce a necessity for change. When this is to take place in the Sphinx, the larva 

 ceases to eat, becomes restless and active, and after forming a cell in the earth lies at 

 rest with its body coiled up, and soon loses the power of locomotion. During this time 

 a contraction of all the longitudinal and diagonal muscles of the body is taking place, 

 particularly of the fourth, fifth, and sixth segments ; and the minute vessels which con- 

 nect the old skin of the larva to the new one of the pupa beneath it are ruptured, and 

 a fluid is effnsed which greatly assists in separating the old from the new covering. 

 The body of the insect is considerably shortened. This contraction occasions a per- 

 manent shortening of the longitudinal muscles, which then gain new attachments, by 

 which portions of each segment of the body, now soft and delicate, are drawn one 

 beneath the other, forming broad duplicatures of the external teguments. This con- 

 traction and shifting of the muscles is carried to such an extent in the fourth, fifth, 

 and sixth segments, as to form a large duplicature around the whole body, and to 

 constitute the future division between the thorax and abdomen. The fifth segment 

 is almost lost in the fourth, and the sixth, the first of the abdomen, is greatly dimi- 

 nished. The third segment is not at all decreased along its dorsal surface. It con- 

 stitutes the greater portion of the thorax. 



By these changes in the tegumentary and muscular structure of the body the gan- 

 glia of the cords are brought nearer together, and confined in their respective places 

 in the segments by the nerves running transversely from them. The cords, from 

 being too long to lie in a direct line, are folded irregularly between the ganglia. The 

 greatest folding and irregularity of the cords is between the fourth, fifth, and sixth 

 ganglia, where, from the almost entire obliteration of two segments, it might justly 

 be expected. A disposition is induced in the first five ganglia to become aggre- 

 gated into one mass, by their impingement upon each other, occasioned by the ap- 

 proximation and union of segments to form the thorax, which is assuming a fixed 

 condition, and becoming the centre of development. It is in this manner that tlie 

 nervous structure appears to be elongated forwards for the enlargement of particu- 

 lai- parts. The cords in the abdomen recover their original direction, but are not 

 much increased in diameter, and the sixth and seventh ganglia entirely disappear, 

 while the ganglia and nerves in the thorax are enlarged, and aggregated into two 

 masses ; the crura of the cerebral ganglia are much shortened, and the optic nerves 

 are at the same time proportionably developed. From these facts we may conclude. 



