HISTORY OF THE WORKS OF CUVIER. 143 



are, fur method, two distinct states : the rafioiitd and the empirical. And as 

 metliod ib' always bound to be natural, when, in onh'r to become so, it has no 

 longer the rational way, it becomes so by the em]>irical way ; when it has no longer 

 tlie known importance of the organs to direct it, it is guided by their constancy. 



II. — CLASSIFICATION OF THE ANIMAL KINGDOM. 



* * * Linnaeus divided the animal kingdom into six ckasses : quadrupeds, 

 birds, rcj^tilcs, fishes, insects, imd worms. No precise limit circumscribed these classes 

 in which the cetacea were found among the fishes ; the cartilaginous fishes among 

 the reptiles ; the Crustacea, the articulated worms, animals which have a true 

 cii"Culation, wei*e ranged among the insects which have none ; and the intestinal 

 worms, the polypes, the infusoria, the mc)llusks, even certain fishes were united 

 and confounded in the class vermes, the last and most chaotic of all. * * 

 Into this class, in effect, Linnaeus had introduced endless confusion, and Bru- 

 guiures left it just as Linnaeus liad done. So little attention was still paid to the 

 internal organization of these animals that the last-named author, for exam})le, 

 taking- for niollusks all that had no shell, se])arates from the class in (question, 

 under the name of testacea, all that have a shell, as if the slight external character 

 of having a shell hindered the testacea from being true mollusks by virtue of their 

 entire nature or internal organization. 



It was in 1795 thatM. Cuvier pointed out the extreme difference of the objects 

 confounded in this class, and separated them distinctly, one from another, after a 

 detailed examination and agreeably to characters derived from their organization 

 itself. This examination produced a new general distribution of animals with 

 tchitc blood into six classes, mollusks, crustaceans, worms, insects, echinoderms, 

 and zoophytes. From this new distribution of the white-blooded animals dates 

 the revolution of zoology. 



Still later M. Cuvier associated the crustaceans with the insects, on account of 

 the common symmetry of their parts, and the articulated structure, alike common, 

 of their memb(n-s and body ; he separated the annelidii, or worms with red blood, 

 from the intestinal worms ; for he pointed out that the former have a true circu- 

 lation, a distinc;t nervous system, an articulated body, while the others have 

 neither circulation nor distinct nervous system, nor body properly articulated. 

 He showed that the mollusks, which have so rich an organization, abrain, eyes, 

 often very complex, sometimes ears, always numerous secretory glands, a double 

 circulation, &c., should in the first place be raised greatly above the ptdyjies and 

 other zoophytes, the greater part of which have not even distinct organs, and 

 with which, nevertheless, they had been so long ranged ; and, in the next place, 

 that the collective assemblage of these mollusks formed a group which, by the 

 importance of its general characters and the number of species which comj)ose it, 

 corresponds not to such or such a class or fraction of the vertebrate animals, but 

 to all the vertebrata joined together ; and then, taking up each of the great masses 

 of the animal kingdom, he saw that scarcely any of the general divisions there- 

 toffu'e admitted could be sustained, at least with the characters and limits which 

 had been thus far assigned to them. For instance, it was customary to op])ose 

 the rertcbratc animals to the animals ivitliout vcrtebrcr, as if these two divisions 

 had l;een of the same rank ; and to designate eipially l)y the name of class the 

 whole of the mollusks and a mere fraction of the vertebrata, as if, in effect, the 

 whole })ody of mollusks was only e(j'iivalent to a fraction or subdivision of the 

 vertebrata, &c. Now, since the infinitely varied organization of the animals 

 without vertebrae was at last known, it was impossible anv longer to pretend that 

 there was not, between all these varied animals, vastly more difference than 

 between certain vertebrates and certain others. But if, of these two divisions, 

 one comprised structures far more varied than the other, the one could not bo 

 equivalent to the other ; they were not of the same rank ; they should not then 



