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 tébia of the first pair of feet two oval apertures, covered by a 
tense membrane, which De Grrr! 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 Acridiwm 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 antenne 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 ona 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?. 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 ErtcHson’s Archiv fiir Naturgesch. 1844, s. 52—81, Taf. 1. 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 Acalephe and Echinoder- 
mata. 
? 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 
