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



respiratory nerve divides and passes on each side the ramifying tracheal vessels as 

 they come from the longitudinal one ; the posterior division forms a very minute 

 plexus at their base, and both distribute some filaments upon the ramifying branches, 

 which appear to be lost in their substance. While the respiratory nerves pass on both 

 sides of these tracheae, a large branch from the gangliated cords, the symmetrical 

 system, passes only on the posterior, and gives off a few filaments to the surrounding 

 muscles in its way round the side of the body to the dorsal muscles. 



c. The ganglia, when just removed from the recently killed insect, are of a 

 more opake colour than the nerves. When placed in alcohol they do not contract 

 in size, but become still more opake, and appear, therefore, in their chemical com- 

 position, more analogous to coagulated albumen, while the nerves, which remain 

 nearly transparent, seem more analogous to fibrin. There is as much uncertainty 

 respecting the ultimate structure of ganglia as of nerves. When macerated in water 

 for a few hours they readily decompose ; the cerebral ganglia much sooner than the 

 others. From this circumstance some have supposed that cerebral ganglia con- 

 tained ventricles, but I have been unable to discover any, although I have searched 

 for them very closely. From the appearance of the ganglia in Papilio l6, Linn., 

 before noticed, it seems probable that a few fibres pass through the ganglia, both 

 longitudinally and transversely, to the body of the insect, and that ganglia are 

 in reality composed of a nodule of grey matter intermingled with, and inclosed 

 among the fibres of the sensitive column. This is further supported by^ the entire 

 disappearance of ganglia, as in the sixth and seventh, during the transformations of 

 the insect, while the nerves which come from these ganglia remain, and then come 

 from the cords. Whatever be the ultimate structure of ganglia, there seems to 

 be some modification of their chemical composition different from that of nerve. As 

 the optic nerves, which are developed during the pupa state, are formed of fibres, 

 there certainly appears reason to suppose that the structure of the cerebral, and con- 

 sequently of other ganglia, is to a certain extent fibrous, whatever be the peculiar 

 arrangement or interchanging of the fibres. 



All the cords and ganglia, but particularly the latter, are profusely supplied with 

 exceedingly minute tracheal vessels, which penetrate the nerves and most internal 

 part of the ganglion. The minuteness of these extremities is such that I have failed 

 to detect them even with a powerful triplet. I have in general used a triplet, or Wol- 

 laston's doublet, in examining these minute structures. 



Having traced the nerves of the Sphinx through all their changes, and examined 

 their distribution and structure as compared with other Articulata, it now remains 

 to show the manner in which the changes which take place in them are induced and 

 effected. 



III. Development of the Nervous Columns. 



a. During the time I was most engaged in watching the development of the Sphinx, 

 in the spring of 1832, considerable difficulties presented themselves, and many 



