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



in the Sphinx, in which the under surface of each joint is encircled by a double ring 

 of exceedingly delicate elastic cilia [Plate XIV. figg. 17, 18. (a)], seems more fitted for 

 feeling, or perceiving the vibrations of the atmosphere, and thereby for performing a 

 function analogous to that of hearing, as has been suggested by Bonsdorf, Camparetti, 

 and other naturalists, than for any other with which we are acquainted. The sense of 

 touch is evidently the primary endowment of the antennae in articulated animals, as 

 seen in the Myriapods ; but this cannot be their use in many insects, Lihellulce, Di- 

 ptera, &c., in which they are short and immoveable, nor in those Coleoptera in which 

 they are terminated by lamellae ; while their structure in almost every class is totally 

 incompatible with the function of smelling. But there is no class in which their 

 structure could incapacitate them for feeling the pulsations of the atmosphere, and 

 thereby performing a function analogous to that of hearing. 



b. Net'ves of Fision. — The compound eyes of insects are parts of great interest, but 

 of difficult investigation. Professor Muller, Straus-Durckheim, and others have 

 carefully examined them, but there is still a difference of opinion respecting their real 

 structure. I have not yet sufficiently examined them to offer an opinion, my attention 

 having been confined chiefly to the development of the optic nerves themselves, during 

 the transformations of the insect. This can only be shown in those insects which have 

 simple sessile eyes in their larva state, and numerous compound ones in their perfect, 

 as in Lepidoptera, Hymenoptera, and some other genera. In the larva of the Sphinx 

 the optic nerves are only two diminutive trunks, extending from the sides of the cere- 

 bral ganglia, and dividing each into eight filaments, given to the eight minute eyes 

 on each side of the head. At the period of changing to the pupa state there is a deposit 

 of dark pigment, very slightly organized, at the base of each nerve. As the changes 

 of the insect advance, the optic nerves gradually enlarge at their base ; and when this 

 enlargement has gone on to a considerable extent, the dark pigment is carried for- 

 wards from the base of the nerves, and exhibits a corrugated appearance around its 

 interior margin. When the changes have further advanced, the optic nerves are ex- 

 tended, of a pear-like form, from the sides of the cerebral ganglia, which they then 

 equal in diameter. The enlargement of the nerves seems to be occasioned by the 

 shortening of the cords which connect the cerebral with the suboesophageal ganglia, 

 and the extension forwards of the nervous substance of the cords within the investing 

 theca, the eff*ect of which is not to enlarge the cerebral ganglia in a corresponding 

 degree, but to develop the optic nerves, by the gradual extension and expansion of 

 the nervous substance within them, in the form of successive series of purse-like 

 layers of fibres [Plate XV. fig. 31. b.] one within the other. When the outer layer has 

 arrived at its maximum of extension, it seems to become perforated at a point corre- 

 sponding to the central part of the membrane, which is carried forward to become 

 the choroid [fig. 31. (c).]. The next layer advances, and then the next in suc- 

 cession from within outwards, so that the central portion of the nerve is the last part 

 developed. The fibres of each series, from being bent like the segment of an arc. 



