382 Royal Sociehj. 



theory, he states, may be extended, without any analytical difficulty, 

 to any power of the disturbing force, or of the eccentricities, ad- 

 mitting the convergence of the series; nor does it seem to be limited 

 by the circumstance of the planet's moving in the same direction. 



A Paper was also read, entitled, " On the Nervous System of the 

 Sphinx Ligiistri (Linn.), and on the Changes which it undergoes du- 

 ring a part of the Metamor|)hoses of the Insect," by George Newport, 

 Esq. Communicated by Peter Mark Roget, M.D. Sec. R.S. 



The author gives a minute anatomical description, accom])aniedby 

 drawings, of the development and arrangement of the nerves of the 

 Spliiux Liguslri, and the successive changes they undergo during the 

 last stage of the larva, and the earlier stages of the pupa state. As 

 this insect, in passing from its larva to its perfect state, remains for 

 several months in a torpid condition, it affords a better opportunity 

 of minutely following these changes, and of ascertaining in what man- 

 ner they are effected, than mostother insects ; and the great compara- 

 tive size of this species renders the investigation still more easy. 



While in its larva state, this insect frequently changes its skin : it 

 enlarges rapidly in size after each operation, and the nervous sy- 

 stem undergoes a corresponding development. The author minutely 

 describes the longitudinal series of ganglia, which extend the whole 

 length of the animal. He remarks that the eleventh or terminal gan- 

 glion is distinctly bilobate, a form which, as suggested to him by Dr. 

 Grant, is probably acquired by the consolidation of two ganglia which 

 had been separate at an earlier period of development. A detailed 

 account is then given of the nerves proceeding from these several 

 ganglia. 



During the change from the state of larva to that of the perfect 

 insect, the number of the ganglia is found to diminish in consequence 

 of the approximation and conjunction of adjacent ganglia; and the 

 nervous cords which connect them are generally much shortened. 

 A nerve is described which, from the mode of its distribution to the 

 stomach, intestinal canal, and dorsal vessel, presents a remarkable 

 analogy to the pur vagum, or pneumogastric nerve of vertebrated 

 animals ; so that the author considers it probable that its functions 

 are somewhat similar to this nerve ; as has, indeed, been already con- 

 jectured by Straus-Diirckheim. Another division of nerves exist, 

 which, from the principal branches derived from each abdominal 

 plexus being always distributed among the trachea, near thespiracles, 

 are perhaps analogous to the sympathetic system of nerves of the 

 higher classes of animals. 



When on the point of becoming a pupa, the nervous lobes above 

 the oesophagus are found to be considerably enlarged, and to have 

 assumed more of the a|)pearance of a cerebral mass ; while, at the 

 same time, the nervous cords descending from them are shortened 

 and thickened. The ganglia are brought nearer together, and their 

 intervening cords lie between them in an irregular manner, the 

 ganglia themselves being retained in their proper places in the 

 segments by the nerves running transversely from them. The 

 nerves of the antennae arc enlarged, and the optic nerves are become 



