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



has disappeared ; and the nerves which came from that also come now from the cords, 

 very near to those of the fifth ganglion, and thus further show that the substance of 

 the ganglion has been transmitted forwards. The seventh ganglion is decreased in 

 size. 



At forty-eight hours [Plate XVI. fig. 29.] the whole of the cords have regained the 

 longitudinal direction, so that there must have been either consolidation, absorption, 

 or elongation forwards of the nervous substance, for the purposes of development. 

 The seventh ganglion has now entirely disappeared. 



At Jifty -eight hours [Plate XVI. fig. 30,] a further change is effected. The second 

 and third ganglia approach and coalesce, and the double ganglion thus formed is only 

 separated from the larger thoracic mass, composed of the fourth and fifth ganglia, and 

 part of the sixth, by very short but much enlarged cords. The transverse plexus are 

 united with the nerves to the wings, and the whole mass of ganglia and nerves have 

 been carried forwards, and lie more in the middle of the thorax. The optic and an- 

 tennal nerves have nearly attained their full development, and the plexus of nerves 

 and ganglia in the thorax, which in the larva exhibit an intricate arrangement, are 

 now united, and form only a few large trunks, which can hardly be recognised as the 

 same structures. The arrangement of the whole nervous system is nearly the same 

 as exists in the perfect insect. Yet all this has taken place at a comparatively early 

 period of the pupa, three days not having elapsed since the insect underwent its 

 metamorphosis. It is interesting to observe that while the nervous system has been 

 thus rapidly progressing, the alimentary canal, generative system, and other organs 

 are still very far from completion, and, as compared with the nervous system, have 

 made but little progress. It therefore seems as if necessary that the nervous system 

 should be first completed. 



These observations upon the Butterfly were made in June 1832, when the length 

 of time that the insect remained in the pupa state was generally thirteen days and a 

 few hours. They were carefully repeated in the following August, when the tempe- 

 rature of the season was considerably higher, and then the insect seldom continued 

 more than nine, and often not more than eight days in pupa ; thus clearly proving 

 the decided influence which increased temperature exerts over development in acce- 

 lerating the latter stages, since I could not discover that the earlier period, during 

 which the changes in the nervous system were taking place, was very much accele- 

 rated by it. 



These observations coincide with those upon the Sphinx. But it is interesting to 

 remark the difference in the length of time which the changes occupy in the two 

 insects, relatively to the length of time which they pass in the pupa state. The But- 

 terfly, during the summer, is scarcely fourteen days, and often not more than eight 

 in the pupa, and very nearly completes its changes in the nerves in three days. The 

 Sphinx, on the other hand, passes nearly nine months in the pupa state, during more 

 than eight of which its nervous system is undergoing change. But it may still be 



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