402 INTRODUCTION TO THE 



sarj'- 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 sjjiders — are, in respect to their organic systems, the most perfectly organized 

 {les plus parfaits) 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 Lerons d' Anatomie Compar^e, 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- 

 illae, 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 Generiques 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 wiU 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 diff'erent 

 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 iwo antennae. The primary groups of insects are founded upon 



