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(as observed by Kirby and Spence) they were used as organs of touch. 
It had been urged by some that they could not well be organs of touch, 
on account of the hard horny character of their outer surfaces, and that 
this function was performed by another set of organs, the pa/fz. 
Many naturalists inclined to the idea that they were the organs of 
hearing. Now it was generally conceded that in the crustacea, es- 
pecially the higher ones, the organs of hearing were situated at the base 
of the long external pair of antennze, and, as in the case of the cray- 
fish, consisted of a hollow cylindrical process, closed internally by a 
drum—a thin membrane, behind which was a vesicle filled with fluid, 
which received the termination of a nerve; but the organ of smell, as 
had been principally observed with crabs, consisted of cavities, lined 
with a mucous membrane, situated at the base of the inner pair of 
antennz, and protected externally by fine bristles. Many observers 
had noticed that if a noise was made the antennze of some insects 
were turned in the direction of the part from which the noise came. 
This had been observed in the case of the longicorn beetles, grass- 
hoppers, and crickets, which, when suddenly surprised by a noise, had 
been seen to stretch out their long antennz and stand, as it were 
attentively listening for the sound. Rennie mentioned a green grass- 
hopper inclining its antennz to the rustle of a piece of paper under 
the table on which it was placed, and bending one of them in the 
direction of the sound. 
On the other hand, many circumstances seemedito prove that insects 
possessed a very acute sense of smell. It had been observed in 
‘- Episodes of Insect Life” that “no flocks of vultures can be directed 
more unerringly to their revolting prey by its odours from afar, 
than certain insects, such as dung-flies and carrion beetles, whose 
corresponding office is to assist in ridding the earth of offensive 
objects.” That it was the sense of smell which directed the blow-fly 
to the deposition of the larvz was shown by the fact that she had laid 
them on s¢afelias, a carrion-odoured hot-house plant, and on silk with 
which tainted meat had been covered. 
Equally keen-scented were butterflies and bees ; the latter had 
flown miles in the direction of particular flowers, whose odour had 
been wafted by the wind, while the former had alighted from a con- 
siderable height on their favourite flowers. 
Then, as was well-known to lepidopterists, night-flying moths were 
attracted from long distances by anointing the trunks of trees with 
sugar or treacle, and this, he should think, by the sense of smell alone. 
