406 
ARTICULATED ANIMALS. 
minute [hexagonal] lenses or facets, to each of which there is a corresponding filament 
of the optic nerve. These two kinds of eyes may exist in conjunction or separately, vary- 
ing in the genera ; and we know not whether their action, when united in the same 
individual, be essentially different. The sense of sight, however, must in all instances be 
effected in a manner quite unlike that of the Vertebrata. (Consult the Memoir of 
Serres on the Eyes of Insects, Montpelier, 1815, 1 vol. 8vo; and the Observations of 
Blainville on the Eyes of Crustacea, in Bull. Soc. Philomat.) [also the memoir of 
J. Muller, conscisely abstracted in the Insect Miscellanies.”] 
Other organs, which we here find, for the first time, amongst the Crustacea and 
Insecta*, and which are named antennae, are articulated filaments, varied in the greatest, , 
degree as to their form, even in the sexes of the same species, arising from the head, 
and appearing eminently endued with a delicate sense of touch, and perhaps, also, with 
some other kind of sensation of which we have no idea, but which has reference to the 
state of the atmosphere. 
These animals also enjoy the senses of smell and hearing. Some authors place 
the seat of the first of these senses in the antennsef ; others, as M. Dumeril, in the 
orifices of the breathing pores ; and others, as M. de Serres, in the palpi. These 
opinions, however, are not founded upon positive and conclusive facts. As to the sense 
of hearing, the Decapod Crustacea, and certain Orthoptera, alone possess a visible ear. 
The mouth of these animals presents a great analogy [or general uniformity] , which 
also extends, according to Savignyf, in a relative manner, even to those species which 
subsist by suction. Those which gnaw their food [Mandihulata, Clairville] by means 
of jaws fit for trituration, have the parts of the mouth arranged in pairs laterally, and 
placed one before [or over] the other. The anterior pair are specially named mandibles, 
[the succeeding pair or pairs being termed maxillse, or hind jaws] ; the pieces which 
cover the jaws before and behind are the lips§, that in front being called the labrum, 
[and that behind being the labium]. The palpi are articulated filaments attached to 
the hind jaws and the hind or lower lip, and appear to assist the animal in 
recognizing its food. The form of these different organs determine [or, more properly 
speaking, indicate] the kind of nourishment with as much precision as the dental 
system of Mammalia. Within the lower lipH, the tongue (ligula) [or rather lingua] 
is ordinarily attached. Sometimes, as in the bees, and many other Hymenoptera, it is 
prolonged considerably, as weU as the maxillae, forming a kind of proboscis (promuscis), 
with the pharynx at its base often covered by a kind of secondary lip {sous-lalre ; 
epipharynx, Savigny), and which appears to me to exist, in many beetles, in the form 
* And even in the Arachnida, but under modified forms, and with 
modified functions. 
t With reference, at least, to Insecta, and when they terminate in 
a more or less complicated mass, or are clothed with a great quantity 
of hairs. According to M. Desvoidy, the internal antennae of the 
Decapod Crustacea are organs of smell {Bull. Set. Nat. 1827), but he 
cites no direet proof; and, indeed, in the most carnivorous crabs 
{Gecarcinus, &c.), where the organ of smell ought to be most fully 
developed, the very reverse takes place, [the inner antennae being 
very small.] 
t Mhnoires sur les Animaux sans FerMres. The original idea [of 
this uniformity] was first announced by me (but without develope- 
ment) in my Histoire Genirale des Insectes. 
§ I here more particularly allude to the Hexapod insects. 
II The labium is protected in front by a corneous piece, formed by a 
cutaneous elongation, and articulated at its base with a part of the 
under side of the head, named the mentum. Its two palpi are termed 
labial palpi. The maxillary palpi are two or four in number, in the lat- 
ter case being named external and internal, tbe internal palpi being a 
modification of the outer lobe of the maxillaj, and which is named 
galea by Fabricius, in Orthopterous insects. In these insects, and in 
the Libellulae, there is a soft vesiculose body in the middle of the 
mouth, distinct from the lower lip, and which, compared with the 
Crustacea, appears to be the true tongue {Labium, Fabr.) This 
organ is probably represented in many Coleoptera by the lateral divi- 
sions of the labium, which are termed paraglossce. The membranous 
terminal part of the lower lip, extending between the palpi in the 
Orthoptera and Libellulas, is quite distinct from this central tongue, 
although nearly all entomologists have termed this terminal extremity 
of the lip by the name of languette. It is, nevertheless, true, that this 
central tongue is often closely soldered to the [inner surface of] the 
lower lip. [The composition of the lower lip is very complicated, 
and variable in different groups. As a whole, it is best to retain for it 
the name of labium. Its corneous basal piece is the mentum. The 
following piece is generally called the labium, having the labial palpi 
arising at its base ; but the German authors term this terminal piece 
ligula. The internal piece is the lingua. Latreille refers to the 
larv® of the Dyticid®, as affording a clear notion of the typical struc- 
ture of the labium ; but in these larv®, the labium is almost obsolete. 
The perfect Silph®, or Staphylini, afford much better instances.] 
