CRUSTACEA, ARACHNIDES, 1NSECTA. 3 



Other organs which for the first time are here presented to 

 us, and which are found in two of these classes, the Crustacea 

 and the Insecta(l), the antennae, are articulated filaments, va- 

 rying greatly in form, and frequently according to the sex, 

 attached to the head, appearing to be peculiarly devoted to a 

 delicate sense of touch, and perhaps to some other kind of sen- 

 sation of which we have no idea, but which may refer to the 

 state of the atmosphere. 



These animals enjoy the sense of smell and that of hearing. 

 Some authors place the seat of the first in the antenn3e(2), 

 others, M. Dumeril for instance, in the orifices of the tracheae, 

 and Marcel de Serres, &c. in the palpi ; neither of these 

 opinions, however, are corroborated by positive and conclu- 

 sive facts. As to the second, it is only in the Crustacea Deca- 

 poda and some few of the Orthoptera, that we can find a visi- 

 ble ear. 



The mouth of these animals presents a great analogy, which, 

 according to Savigny(3), and at least with respect to the Hex- 

 apoda, extends to those which can only feed by the suction of 

 liquid aliment. 



Those called Tritores or Grinders {broyeurs), on account 

 of their having jaws fitted for triturating their food, always 

 present them in lateral pairs, placed one before the other ; the 

 anterior pair are especially called mandibles; the pieces which 



(1) And even in the Arachnides, but under different forms, and with different 

 functions. 



(2) As regards insects, and when they are claviform, or terminate in a club 

 more or less developed, or furnished with numerous hairs. According to M. 

 Robineau Desvoidy, the intermediate antennje of the Crustacea Decapoda are the 

 olfactory organ, Bullet, des Sc. Nat.; but he adduces no one direct experiment in 

 proof of his opinion. It would, if this were so, seem probable that in the highly 

 carnivorous Crustacea, such as the Gecarcini and others, we should find this organ 

 in a comparatively greater state of development, whereas the fact is directly the 

 reverse. His ideas respecting the external composition of the Crustacea Decapoda 

 suppose the existence of a skeleton. He should have commenced, however, by 

 establishing the connexion of these animals with the Fishes, and not by admitting, 

 as a positive fact, what is at least a- matter of doubt. 



(3) MSmoire sur Its animaux sans vertebres. The original idea was thrown out, 

 but undeveloped, in my Hist. Gen. des Insectes. 



