246 
Mr. G. Newport on the 
deed the case appears the more probable from observations made 
both by Scarpa and Fabricius on the anatomy of the setaceous 
antennae of the cray-fish, Astacus Jluviatilis , Leach. Those natu- 
ralists found that the tympanum, or seat of hearing, was within 
the head, at the base of the antennae, along the hollow cavities of 
which (and which appear to bear some analogy to the tracheal 
tubes in the antennae of the ichneumon) they believed the sounds 
to be conveyed. Now this opinion is supported by the use which 
is made of the recently invented instrument, the stethoscope, 
which is simply a wooden tube, employed by the physician, by 
interposing it between his ear and the object to be examined, for 
the purpose of concentrating sounds and enabling him to judge of 
them with greater precision. Since then the seat of hearing in 
Crustacea is at the base of these organs, we may thence reasonably 
conclude that it is placed in a like situation in all insects with 
setaceous and filiform antennee ;* but it may still be objected that 
there are species with antennae so formed as to make us doubt 
whether it be not by other than the means of a tympanum that 
they are rendered sensible of sound or atmospheric vibrations ; 
and whether the true seat of hearing may not be differently placed 
in different forms of these organs ? Since elasticity and delicate 
nervous organization are absolutely necessary qualities of the 
parts employed in hearing, may not the elastic cilice, with which 
many antennap are covered, be so delicately constructed as to 
serve for this purpose ? If this be not really the case, how are 
we to explain their use in many insects, particularly in the Pha- 
lcence-\ and some Muscce ; and what reason shall we be able to 
assign for the antenna* differing so much in this respect in the 
male from the female ? By admitting that the ciliae in these in- 
sects perform an office analogous to that of the tympanum in 
others, the difficulty is overcome, and we see at once a reason 
why the antennae of the males in all insects are more developed 
than in the female, and also why some species have them larger 
than others. 
* The Rev. F. W. Hope has recently stated to me his belief that the organ of 
hearing is situated in some species at the base of the first or second joint, and this 
appears highly probable when the occasional large size of these parts is consi- 
dered. Compare also the remarks of Burmeister, Manual of Entomology, trans- 
lated, 1836, pp. 295, 296. 
t According to Burmeister (Manual of Entomology, translated by W. E. 
Shuckard Esq., 1836, p. 2951, G. R. Trevrianus has described the organ of hear- 
ing in moths as consisting of a thin drum situated in the forehead at the base of 
each antenna, but this structuie is not found in all insects of other orders. Com- 
parette also appears to have made similar observations in some species. 
