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namely, being destitute of wings. Fabricius classed the Linnsean Aptera in 

 various sections, but still considered them genuine insects. Cuvier was the first 

 naturalist who held a different opinion. By his elaborate researches in Com- 

 parative Anatomy, he demonstrated that the Crabs and other allied genera 

 (Cancer, Oniscus, and Monoculus of Linn.) "could not be retained amongst 

 insects, inasmuch as they possessed a totally distinct system of respiration, 

 breathing by means of bronchiae, or gills ; as well as a complete system of circu- 

 lation : of these, therefore, he formed the class Crustacea, which has been regarded 

 as distinct by all subsequent entomologists." — Westw., Intr., p. 2. 



Lamarck established on similar grounds another class, which he denominated 

 Arachnida, and which included the Linnsean genera Aranea, Scorpio, Phalangium, 

 Acarus, Scolopendra, Julus, Lepisma, Podura, and Pediculus. 



Latreille (in his last system) regarded the Centipedes (genera Scolopendra, 

 Jidus, Linn.) as constituting a distinct class, which he denominated Myriapoda. 

 He adopted Cuvier's Crustacea, and Lamarck's Arachnida, with the exception 

 of Podura and Lepisma (ord. Thysanura, Latr.), and Pediculus (ord. Parasita, 

 Latr.), which he considered as true insects, and raised to the rank of orders. 



Dr. Leach's system, with regard to the animals in question, differed little from 

 Latreille's. Under his Insecta Ametabola he classed Thysanura (Latr.) and 

 Anoplura (Parasita, Latr.). Leach considered the Mites as a distinct class, 

 which he named Acari. 



Kirby and Spence divided the sub-kingd. Annidosa into three classes : Crus- 

 tacea (Cuv.), Arachnida (Lam.), and Insecta (Linn.), and included under the 

 last the Lepismce, Pediculi, Acari, and Centipedes ; joined together under the 

 single order Aptera, and characterised by respiring by tracheae, and having no 

 system of circulation. This classification is so objectionable, that it was likely 

 to attract Mr. Westwood's notice : he remarks, accordingly, that 



" The incongruous character of the groups thus associated together; the possession of the pul- 

 monary sacs by Thelyphonu's, which is thus placed amongst the Mites; the recent researches of 

 M. Duges on the respiratory organs of Dysdera and Segestria (clearly demonstrating that the 

 respiratory system in Arachnida is not entitled to pre-eminence as a character of this class) ; and, 

 lastly, the admission of Messrs. Kirby and SrEXCE themselves, that their order Aptera is not a 

 natural, but merely a provisional one, and that the hexapod insects are to be regarded as more 

 peculiary entitled to the denomination of insects, will, I trust, be considered as sufficient to au- 

 thorise me in not adopting their views." — p. 3. 



" Our system," says Dr. Burmeister, " is not acquainted with an order 

 Aptera, which we have found in the majority of the others, as in every case it is 

 artificial, and must embrace insects of the most dissimilar orders. The most 

 distinct proof in support of this assertion is furnished by the circumstance that 

 we find in the same family, winged and apterous genera contiguous together, and 

 indeed, in many genera, the males winged, and the females apterous." He has 



