OF THE ANNULOSA. 383 



Insects, under which denomination I include the Ameta- 

 hola, are well known to have their trachea? disposed in a 

 double longitudinal series. 



Linnaeus does not appear to have allowed the existence 

 of antenna? in Spiders or Scorpions, although he assigns 

 this name to certain organs in Nymphon, Phalangium and 

 Chelifer*, which evidently correspond with those organs in 

 Spiders, which he terms their Palpi. The separation of the 

 class of Arachnida from other Annulose animals originated 

 with Lamarck, who nevertheless made it comprehend the 

 Ametabola under the name of Arachnides autennees, as 

 well as the true Arachnida, which, adopting the opinion 

 of Degeer, he entitled "Arachnides exantenntes." M. La- 

 treille in the Genera Insect orum made these latter the 

 third legion of his Insecta, under the name of Acera, and 

 at last, in the third volume of the Regne Animal, com- 

 prised them all in a class entitled Arachnides, which he 

 says " se distingue au premier coup d'ceil des deux classes 

 voisines, les Crustaces et les Insectes, parcequ 'elle n'a -point 

 d'antennes." Still more recently however, in a very sin- 

 gular Memoire presented by him to the Institute, he has 

 advanced several curious speculations on the external or- 

 ganization of Winged Insects, as compared with that of 

 the Arachnida and Crustacea. Among these theoretical 

 novelties we find that he now considers the old opinion of 

 Lamarck, to wit, that the Arachnida are destitute of an- 

 tenna?, to be an error which he acknowledges to have him- 

 self propagated from not having sufficiently examined the 

 subject. He observes that the mandibles, maxilla? and 

 maxillary palpi, or the organs which correspond to these 



* This genus, or rather Obisium, is so well described by Aristotle, under 

 the epithet of Scorpodes, that 1 think he has the right of priority to the 



