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. Miiller, 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. 



'lliese animals also enjoy the senses of smell and hearing. Some authors place 

 the seat of the first of these senses in the antenneef; 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 SavignyJ, in a relative manner, even to those species which 

 subsist by suction. Those which gnaw their food [Mandibulata, 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 lip||, the tongue (ligula) [or rather lingua] 

 is ordinarily attached. Sometimes, as in the bees, and many other Hymenoptera, it is 

 prolonged considerably, as well as the maxillae, forming a kind of proboscis (promuscis), 

 with the pharynx at its base often covered by a kind of secondary lip (sous-labre ; 

 epipharynx, Savigny), and which appears to me to exist, in many beetles, in the form 



* And even in the Arachnida, but under mortified 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. 1327), but he 

 cites no direet proof; and, indeed, in the most carnivorous crabs 

 (Gecncirius, &c.)» where the organ of smell ought to be most fullv 

 developed, the very reverse takes place, [the inner antennae being 

 very small. J 



t Memoires sitr les Animauf satis VertPbret. The original idea [of 

 this uniformity] was first announced by me (but without develope- 

 rnent) in my Histoire Generate des Insectes. 



§ I here more particularly allude to the Hexapod insects. 



|| 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 

 labia] palpi The maxillary palpi are two or four in number, in the lat- 

 ter case being named external and internal, the internal palpi being a 

 modification of the outer lobe of the maxilla;, and which is named 



galea by Fabricius, in Orthopterous insects. In these insects, and in 

 the Libeliulae, 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 bv the lateral divi 

 sions of the labium, which are termed paraglossia. The membranous 

 terminal part of the lower lip, extending between the palpi in the 

 Orthoptera and Libeliulae, 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 surfece 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 piecj 

 iigula. The internal piece is the lingua. Latreille refers to the 

 larvae of the Dyticidae, as affording a clear notion of the typical struc 

 ture of the labium ; but in these larva?, the labium is almost obsolete. 

 The perfect Silphae, or Staphylini, afford much better instances.] 



