129 



is also no less important, on the other hand, to complete, in the latter, 

 the method hitherto applied solely to the periodic inequalities. Hi- 

 therto those terms in the disturbing function which give rise to the 

 secular inequalities, have been detached, and the stability of the 

 system has been inferred by means of the integration of certain 

 equations, which are linear when the higher powers of the eccentri- 

 cities are neglected ; and from considerations founded on the varia- 

 tion of the elliptic constants. But the author thinks that the stability 

 of the system may be inferred also from the expressions which result 

 at once from the direct integration of the differential equations. The 

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

 ring a part of the Metamorphoses of the Insect," by George Newport, 

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



The author gives a minute anatomical description, accompanied by 

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

 Sphinx Ligustri, 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 most other insects; and the great compa- 

 rative 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 ac- 

 count 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 par 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-Durckheim. Another division of nerves exist, 

 which, from the principal branches derived from each abdominal 

 plexus being always distributed among the tracheae, near the spiracles, 

 are perhaps analogous to the sympathetic system of nerves of the 

 higher classes of animals. 



