INSECTS. 283 



readily seen, that it is not very possible in all cases to determine 

 by anatomical investigation the situation of this organ. VON 

 SIEBOLD not long ago thought he had discovered in Orthoptera an 

 auditory organ which is not in the head. In Locusta there are on 

 the tibia of the first pair of feet two oval apertures, covered by a 

 tense membrane, which DE GrEER 1 had already figured. Behind 

 this there is a vesicular expansion of the air- tube of the fore-feet 

 and at its anterior margin a nerve, which coming from the first 

 thoracic ganglion, spreads out into a band-like swelling in which 

 oval, granular bodies, together with long pediculated, remarkable 

 rods, are contained. In Acridium and Truxalis there is situated in 

 the first segment of the abdomen, on each side above the third pair of 

 feet, a tense membrane, behind which there is a vesicle filled with 

 a clear fluid: this vesicle is surrounded by an air-sac, and to it 

 there runs a nerve from the third thoracic ganglion, which is also 

 swollen, and in the swelling exhibits similar rod-like bodies to 

 those which in Locusta occur in the nervous swelling of the fore- 

 feet. 



There still remains something to be said by us respecting the 

 organs of motion in Insects. The antenna of insects are attached 

 to the horny covering of the body, which forms an external frame- 

 work, a dermal skeleton. This ought not on that account, as has 

 sometimes happened in consequence of incorrect and confused notions, 

 to be. put on a par with the skeleton of higher animals ; for the bones 

 or cartilages which form the framework of vertebrate animals belong 

 for the most part to the neural skeleton, that is, the most essential 

 and central parts that compose the column of the vertebral skeleton 

 protect the spinal cord and brain and separate them from the 

 rest of the body 2 . Yet there are parts present in Insects which 



1 For a more detailed description I refer to the observations of VON SIEBOLD him- 

 self in EBICHSON'S Archivfur Naturgesch. 1844, s. 52 81, Taf. i. With every con- 

 sideration for SIEBOLD'S great merits in the anatomy of the lower animals, I venture to 

 express modestly my doubts that in insects organs of sense can occur in such an 

 unusual situation. The eyes on the margin of the mantle in Pecten and Spondylus 

 afford little support to this view, inasmuch as the type of the acephalous molluscs, has 

 just as little claim to the possession of a head, as that of the Acalephce and Echinoder- 

 mata. 



2 It is a merit of CARUS well deserving of acknowledgement, that he recognised 

 and clearly defined the difference between the dermal, the visceral and the nervous 



