126 MEMOIE OF CUVIEE. 



Hitherto M. Cuvier Lad seen, in eacli of these grand dasses of invertebrate 

 animal;?, molJusl^s, insects and zoophi/fes, only a group like each of the four 

 classes of vertebrate animals, qnadnqjcds, birds, reptiles and fishes. It was 

 because he had as yet considered only the organs of circulation. 



In considering the nervous system, whicli is a much more important organ, he 

 saw that each of the three great classes of animals without vertebra? corresponded 

 or \\'as equivalent not to such or such a. class of veriehrafe animals tahen sepa- 

 rateh', but to all these vertebrate animals taken together. A first form of the 

 nervous system unites all these vertebrate animals in a single group ; a second 

 form unites all the niollusks ; a third unites the insects to the wonns with red 

 blood, and both to the Crustacea, constituting the group of articulata ; a fourth 

 form, finally, unites all the zoophj^tes. There are thus four plans, four types in 

 the animal kingdom, ibur emhranehements, as M. Cuvicr calls them ; or, in plainer 

 terms, and divested of everything vague, there are four general forms of the 

 nervous system in animals. 



In the sciences of observation and experiment the supreme art of genius is to 

 transform questions from simple (questions of reasoning into questions of fact. 

 For more than a century' the question had been debated whether, in animals, 

 there was but one ]ilan of oiganization, or whether there were several. This 

 question, couched till then in terms so vague, is transformed by M. Cuvier into 

 this other question, positive and to the point, nameh', how many distinct forms 

 are there of the nervous system in animals? Now, as I have just said, there are 

 lour- — one for tlie vcrtehrafa, one for the mollusca, one for the artictdata, one for 

 the zoophyta ; these four plans or types comprising the whole animal kingdom. 



Sucli is the liglit thi'own upon the animal kingdom by the great Avork under 

 consideration that, guided l)y this, the mind is enabled precisely to apprehend 

 the different orders of relation which connect animals with one another; the 

 relations of conformity (d'cnsemhlej which constitute the unity, the character of 

 the kingdom ; the relations more or less general which constitute the miity of 

 the emhranehements, of the classes; the more particular relations which constitute 

 the unity of the orders, of the genera. 



Nevertheless, this work of so vast a scope, of such immense detail, was not 

 yet what IM. Cuvicr would have A\ished. It is the property of genius always to 

 see something beyond and better than all that it has done. And, indeed, though 

 all tlie species had been reviewed in this great work, the greater part of them 

 had been scarcely more than indicated ; it was, therefore, ouly an abridged, not 

 a complete system of animals. No^^', the idea of a corajjlete system of animals, 

 a system in whicli all the species should be not only indicated, distinguished, 

 classified, but represented and described in their whole structure, was one of 

 those with which M. Cuvier Avas most constantly occupi(Kl. Hence, scarcely 

 was this great treatise on the animal kingdom terminated, when anothei" was 

 already commenced, and on a plan not less vast. I niean the '' Natural History 

 of Fishes," ( HisuAre ncdureUe des poissons,) the first volume of which appeared 

 in 1828. 



After having effected, in the earlier of these two works, the complete reform 

 of tlie system of animals, what he had wished in the second was to show, by a 

 detailed and thorough exposition of all the known species of a class, what could be 

 done for all other species and all other classes. With this view he had chosen 

 the class of fishes as being, aniong all those of the vertebrata, the most numerous, 

 the least known, and that most enriclied by the recent discoveries of travellers. 

 The latest aitthors of note in ichthyology, Bloch and Lacepede, were scarcely 

 acquainted with so many species of fish as 1,400 ; in the work of M. Cuvier 

 the number of species would have amounted to more than 5,000 ; the entire 

 work would have included not less than 20 volumes, all the materials wen? placed 

 in order, and the nine volumes winch made their appearance in less than six 

 years full}' attest the Avouderful rapidity with which it was intended that this 

 vast undertaking sliould proceed 



