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XIX. On the Nervous Si/stem of the Sphinx ligustri, Linn., (Part II.) during the 

 latter stages of its Pupa and its Imago state ; and on the Means hy which its Deve- 

 lopment is effected. By George Newport, Esq. Communicated by P. M. Roget, 

 M.D. Sec. R.S. 



Received March 6, — Read June 19, 1834. 



AN a former paper * I have described the anatomy of the nervous system of the 

 Sphinx ligustri, Linn., and the changes it undergoes during the larva and the earlier 

 stages of the pupa states. In the paper which I now have the honour of laying be- 

 fore the Society, these changes will be followed through the remaining stages, until 

 the insect has arrived at its full development, and I shall endeavour to show the 

 manner in which they are effected. 



I. 1. Of the Pupa. 



We have seen that the nervous system of this insect, during the larva state, is com- 

 posed of two cerebral ganglia which lie above the oesophagus and dorsal vessel, and 

 eleven ganglia, connected by intervening cords, disposed along the median line of the 

 body, below the oesophagus and alimentary canal. These ganglia and cords undergo 

 considerable changes, both in number, situation, and form, when the insect has entered 

 its pupa state of existence. After these changes have been carried to a certain extent, 

 they appear to be suspended for several weeks, during which the insect remains in 

 a state of hybernation. At the expiration of that period the changes again proceed, 

 and are continued uninterruptedly until the insect has arrived at the perfect state. 



In the month of March, when the pupa is becoming more active, all the ganglia of 

 the body are very distinct, and the optic nerves, which proceed from the supra-oeso- 

 phageal ganglia, and which are soon to equal them in size, are beginning to be en- 

 larged at their base. [Plate XIII. figg. 1 and 2.] The ganglia of the head and thorax 

 have undergone the most alteration. If the nervous system be closely examined at 

 this period, it will be seen that these ganglia and nerves give evidence of still further 

 change. The nerves which supply the wings, and which, up to this period, are each 

 formed by two roots, — one derived from the cord, and one from the ganglion attached 

 to it, as shown in the larva state in my former paper, — are increasing in size, particu- 

 larly at their base [fig. 2. b.] ; while the anterior pair of nerves from the second gan- 

 glion, which unite with the second pair from the same ganglion, now originate from 

 the cords, preparatory to the subsequent change in situation of the ganglion itself. 



* Philosophical Transactions, 1832, p. 383. 

 MDCCCXXXIV. 3 E • . 



