824 $ 276. 
nally, these organs are lined by a soft membrane, which contains a nerve 
‘arising from the brain in common with the internal antennal nerve. © 
§ 276. ) 
Organs of Hearing, with the Crustacea, have as yet been observed only 
with the Decapoda.” With these Crustacea, there is a hollow conical pro- 
cess, perforated at its obtuse apex, on the lower surface of' the basal joint of 
the external antennae. Its opening is always closed by a kind of Tympa- 
nitic membrane, in the centre of which there is usually a fissure. Behind 
this conical process, and in the cephalothorax, there is a large, thin-walled 
sac, filled with a clear liquid; this is prolonged by a kind of neck into the 
process, and has, undoubtedly, the function of a Labyrinthus,® for, a 
special nerve, arising from the lateral parts of the brain, in common with 
THE CRUSTACEA. 
the external antennal nerve, is spread upon its walls. 
The base of this labyrinth is in convection with a singular glandular 
organ, of a usually greenish color, but whose nature is yet undetermined. 
1 These olfactory organs were first described and 
considered as such by Rosenthal (Reil’s Arch. X. 
1811, p. 433, Taf. VIII. fig. 1-4) with the craw-fish 
and lobster. Treviranus (Bivlugie, VI. 1822, p. 
308) has subsequently confirmed these observations 
with the lobster. See, for this same animal, Miine 
Edwards, Hist. Nat. d. Crust. Pl. XII. fig. 1. 
These organs have been found latterly, also, by 
Farre, with Palinurus and Pagurus, (Philos. 
Trans. 1843, p. 233, Pl. IX. X. and Ann. of Nat. 
Hist. XII. p. 229). Ihave myself observed them 
with Palaemon, Nephrops, and Maia. It is diffi- 
cult to understand how Farre could have taken 
these cavities for organs of hearing into which 
grains of sand, entering by accident, would serve 
as otvlites, : 
1 Although special auditive organs have not yet 
been observed with the other Crustacea, yet it 
cannot be denied that they are sensible to sounds. 
At least, the observations of Coldstream (Cyclop. 
of Anat. I. p.688) show that the Cirripedia have 
avery acute sense of hearing, for they appear 
cognizant of the slightest sound, and quickly close 
the shell. 
2 This cylindrical protuberance, with its tym- 
panitic membrane, is easily seen in the basilar ar- 
ticle mentioned, with Homarus, Astacus, Ne- 
Phrops, Palinurus, and other Macrura ; — see 
Scarpa, Anatom. disquis. de auditu et olfactu. 
p. 2, Tab. IV. fig. 4, a. b.; Weber, De aure animal, 
aquatil. p, 8, 106, Tub. I. fig. 1, No.1, and Milne 
Edwards, Hist. Nat.d. Crust. Pl. XI. fig. 11, 0, 
(Astacus). This protuberance is long and cylin- 
drical with Pagurus striatus, and Homola Cu- 
viert. 
With the Maiina, whose antennal articles are 
large and immovable, the auditive organs are 
slightly protuberant, and situated near the mouth. 
See Savigny, Descrip. de I’Egypte, loc. cit. Pl. 
VI. fig. 4.2 and 6.2 a. e. (Maia and Stenorhyn- 
chus), and Milne Edwards. loc. cit. I. p. 268. Pl. 
IIL. tig. 2, e. Pl. XV. fig. 2, 10,16 (Mata, Mith- 
raz, Leucippa, and Camposcia). 
.With Scyllarus latus, whose antennae are very 
large and fixed at their base, the large but flat 
have found the same concealed in the semilunar de- 
pressions which are underneath the mouth. With: 
Maia, these cylinders are obliquely truncated, and 
are articulated with the large and basilar articles 
of the antenne. They can be depressed towards 
the inner side, and then righted as a kind of ex- 
ternal auditive conch, and for this purpose the in- 
ternal surface of the cylinder has a pair of mus- 
cles which ave inserted on an internal, stirrup-like 
process ; see Cavolini, Abhandl. tiber die Erzeu- 
gung d. Fische und der Krebse, p. 133, and Milne 
Edwards, Hist. Nat. d. Crust. L. p. 124, Pl. XII. 
fig. 10, e. 1. m., and fig. 11, or in Cyclop. of Anat. loc. 
cit. p.768, fig. 397, 398. Further researches are nec~ 
essary, before the opinion of Souleyet (Froriep’s 
neue Notiz. XXVIII. p. 84) can be admitted, that 
asmall,round, glittering body which, with Leucifer, 
is situated at the base of the internal antennae, is 
an auditive organ.* a 5 
3 Formerly, the attention had been called only to 
the portion of this labyrinth which is concealed in 
the auditive cylinder (Scarpa, loc. cit. Tab. IV. 
fig. 6, and Weber, loc. cit. Tab. I, fig. 2). It is. 
only lately that it has been shown that this small 
auditive vesicle belongs to a very large ampulla sit— 
uated at its base ; see Brandt, Mediz. Zool. II. p. 
64, Taf. XL. fig. 18, a. a., and Veuwyler, Anatom. 
Untersuch. tiber den Flusskrebs, in the Verhandl. 
d. schweizer. Naturf. Gesellsch. bei ihrer Versam- 
mel. zu Zurich, 1841, p. 176. 
4 Scarpa, lov. cit. Tab. LV. fig. 5, g. g., and We- 
ber, loc. cit. Tab. I. fig. 2, No. 7; Brandt, and 
Neuwyler, loc. cit.; Farre, Philos. Trans. 1843,, 
Pl. IX. fig. 10, e.e. 
5 This glandular body which appears to be pres- 
ent with the Brachyura also, is situated, with the 
Astacina, behind the base of the external antennae, 
concealed in the lower portion of the shell, and 
covered, in part, by the membranous labyrinth ; see 
Roesel, loc. cit. p. 322, Tab. LVIII. fig. 9, c.3 
‘Suckow, loc. cit. p. 55, Taf. IX. fig. 2, a.; Brandt 
Mediz. Zool. p, 64, Taf. XI. fig. 8,k. (Astacus), 
Miine Edwards, Hist. Nat. d. Crust. Pl, XII. 
fig. 9, a. 10, g. (Astacus and Maia). Neuwyler 
has given the green glands of the craw-fish a spe- 
auditive cylinders are very short and near h 
cial ex jon (loc. cit.). He found that they 
on the borders of the mouth (Savigny loc, cit. Pl. 
VIL. fig. 1.0, a. e.). With Scyddarus arctus, L 
* [§ 276, note 2.) The organ of hearing in Leu- 
cifer first noticed by Souleyet, has since been 
studied by Huzrley (Ann. of Nat. Hist. 1851, p. 
804) who appears to have clearly made out the 
structure which resembles the ordinary form of 
consisted of an intestinoid tube communicating 
with the membranous labyrinth. At first he 
auditory apparatus in the Mollusca. See also 
Schédler (Wiegmann’s Arch. 1846, p. 363) upon 
this organ with Acanthocercus rigidus ; finally, 
Darwin, loc. cit. Cirripedia, p. 63. — Ep. 
