402 INTRODUCTION TO THE 



sary modifications, which have served as the basis of other subsequent classifications. 

 He at first characterized insects from other invertebrated animals, by more rigorous 

 characters than had been before employed, — namely, a knotted or ganglionated nervous 

 chord, extending down the body, and articulated limbs. Linnaeus terminated his class 

 of insects with those which are destitute of wings, although some of them — as the 

 crabs and spiders — are, in respect to their organic systems, the most perfectly organized 

 (les plus par/aits) of the class, and consequently the nearest to the molluscous animals. 

 This arrangement is therefore opposed to the natural system; and M. Cuvier, by placing 

 the Crustacea at the head of the class, succeeded by the other apterous insects, has 

 rectified the method in a point where the series was in opposition to the scale formed 

 by nature. 



In his Lecons d'Anatomie Compulse, the class of insects, after the removal of the 

 Crustacea, was divided into nine orders, founded upon nature, or the functions of their 

 mouth-organs, and the variations in their wings, thus uniting the principles of the 

 Linnaean and Fabrician arrangements. [1st. Those with maxillae, five orders : Gnath- 

 aptera (including the majority of the Linnaean Aptera, after the removal of the Crustacea), 

 Neuroptera, Hymenoptera, Coleoptera, and Orthoptera ; and, 2nd, those without max- 

 illa?, four orders : Hemiptera, Lepidoptera, Diptera, and Aptera.] The groups esta- 

 blished by Cuvier in his Gnathapterous order are nearly identical with those which I 

 proposed in a Memoir presented to the Societe Philomatique, in April, 1795, and in my 

 Precis des Caracteres Grnt'riques des Insectes, in which I divided the Linnaean Aptera 

 into seven orders: — 1. Suctoria ; 2. Thysanura ; 3. Parasita ; 4. Acephala (the Arach- 

 nides palpistes of Lamarck); 5. Entomostraca; 6. Crustacea; 7. Myriapoda. 



Lamarck's arrangement of the Linnaean Aptera appears, however, to make the nearest 

 approach to a natural system; and we have adopted it, with certain modifications, which 

 we will now explain. With him, I divide the Linnaean insects into three classes : — 

 Crustacea, Arachnida, and Insecta ; but I do not employ the characters derived 

 from metamorphosis; — these, although natural, and already employed by De Geer, not 

 being classical {classique), presupposing the observation of the animal in its different 

 states, which has been so much neglected. I have not, however, entirely neglected 

 these characters ; and, indeed, a Memoir which I have prepared upon the metamor- 

 phoses of insects, not yet published, has been resorted to in the general observations 

 upon the different groups. 



In the class Crustacea, I have established five apparently natural orders, founded 

 upon the situation and form of the branchiae, the manner in which the head is articu- 

 lated with the thorax, and the mouth-organs ; and I have terminated this class, like 

 Lamarck, with the Branchiopoda, which are a kind of Crustaceous Arachnida. 



In the class Arachnida, I only comprehend the Arachnides palpistes of Lamarck, 

 and which thus constitute a group well characterized, both internally [from the struc- 

 ture of their respiratory apparatus] and externally, from their being destitute of antennae, 

 and have ordinarily four pairs of feet. I divide this class into two orders : namely, the 

 Pulmonaria and Trachearia. 



The class of Insecta is characterized in a very simple manner by the system of res- 

 piration consisting of two air tubes running along the sides of the body, furnished at 

 intervals with centres of ramifications, corresponding with the [external] spiracles, and 

 by the possession of jwo antennae. The primary groups of insects are founded upon 



