390 MR. NEWPORT ON THE NERVOUS SYSTEM OF THE SPHINX LIGUSTRT. 



By the middle of April, great progress has been made in the changes which are 

 taking place in all parts of the pupa. The respiratory organs have undergone much 

 alteration ; the tracheae which ramify among the muscles of the thorax being extended 

 in calibre, while some of those from the spiracles along the sides of the abdomen have 

 been gradually developed into pulmonary sacs, which are now of considerable size. 

 Of these there are four upon each side of the body, the anterior ones being much 

 the largest, while the tracheae in the succeeding segments are also enlarging. The 

 dorsal vessel [Plate XIV. figg. 11. 12. and 13. (a, a, «)] has become a much firmer 

 structure ; its valves {b), the muscles attached to it, and the many vessels which enter 

 it laterally, and carry the circulatory fluid, are more distinct, and its division into 

 several arterial trunks at its termination, anterior to the cerebral ganglia, [fig. 12. 

 (/*),] is now more easily traced. The muscles of the thorax are also more deve- 

 loped, and certain processes which at first are soft and delicate, and which during 

 the previous months have been in the progress of formation, have now become hard 

 and of a dark colour, like the exterior of the pupa-case. Four of these processes exist 

 along the under surface of the thorax [Plate XIV. fig. 1 . {t, w, v, x)'] . They are deve- 

 loped, as we shall hereafter see, from the duplicatures, or folds, into which the integu- 

 ments of the thoracic segments are thrown cit the period of assuming the pupa state. 

 The anterior one forms the division between the head and collar ; the second, [fig. 1. 

 (I?),] between the collar and thorax, and is posterior to the first pair of legs ; the 

 third traverses the thorax, [fig. 1. (z/),] and serves as an attachment for some of the 

 principal muscles; and the fourth, [fig. 1. (0,] or posterior one, is that which in 

 future will constitute the division between the thorax and abdomen, and even at this 

 period of development, before there has been much deposition of earthy matter to form 

 the covering of the future insect, it is continued around the whole segment, and is of 

 firm but transparent texture. By means of these processes we may clearly indicate the 

 situation of the thoracic ganglia at this stage of development. The second suboeso- 

 phageal ganglion lies between the first two processes, immediately anterior to the 

 first pair of legs. The third ganglion is opposite to the second pair of legs, and ante- 

 rior to the third process. The fourth and fifth ganglia lie between the inferior pair of 

 wings (z) and third pair of legs {k), and constitute one mass, which is situated just 

 behind the third process. The sixth ganglion (m) is separated from the fifth only 

 by a short extent of cord, is very much decreased in size, and is altered from a 

 circular to an oval form. It is situated upon or immediately behind the division 

 between the thorax and abdomen. The nerves from this ganglion are still disposed 

 irregularly, as at the period of transformation, and the longitudinal cords, which are 

 continued from it into the abdomen, have the ganglia situated as in the previous 

 stages of the pupa. 



By the second week in May the future exterior of the perfect insect begins to be 

 formed beneath the common covering of the pupa-case, and in each segment of the 

 abdomen, along the upper surface, on both sides of the dorsal vessel, there is a little 



