260 History of Conchology . 



of Cuvier's labours was happily very different. In 1788, when he was 

 scarcely nineteen years of age, circumstances fixed Cuvier for a time 

 at Caen in Normandy. His sojourn on the borders of the sea indu- 

 ced him, already an enthusiast in natural history, to study marine ani- 

 mals, more especially the mollusca, and the anatomies of them which 

 he now made conducted him to the developement of his great views 

 on the whole of the animal kingdom. With unwearied zeal he col- 

 lected the materials which were at no distant date to become the 

 basis of a classification which run through all its details in a harmo- 

 nious pai'allelism with the developement of organization, so that 

 the student of it when in search of the name and place of the object 

 in his hand was necessitated simultaneously to acquire a knowledge 

 of its principal structural peculiarities, on which, again, as Cuvier 

 beautifully explained, all its habits in relation to food, to habitation, 

 and to locomotion were made dependant. The Linnsean system of 

 avertebrated animals, even in its primary sections, rested on a single 

 external character. The Insecta were antennulated, and the Vermes 

 were tentaculated avertebrates. Had the character been constant 

 or even general, it might have had some claim for adoption, but to 

 a want of constancy was added the fundamental defect of its inap- 

 preciable influence over the organisms of the body. Cuvier's object 

 being to give us not merely a key to the name, but to make that key 

 open at the same time a knowledge of the structure and relations of 

 the creature, such arbitrary assumption of a character was to him 

 useless. After innumerable dissections had made him familiar with 

 many structures, and after a careful consideration of the respective 

 value of characters, as shown in their constancy and influence on the 

 economy of the species, Cuvier resolved to divide the animal king- 

 dom, not as hitherto into two, but into four principal sub-kingdoms, 

 drawing their lines of separation from differences exhibited in the 

 plan on which their muscular, their nervous, and their circulating 

 systems were formed. " There exist in nature," he says, "four prin- 

 cipal forms, or general plans, according to which all animals seem 

 to have been modelled, and the ulterior divisions of which, whatever 

 name the naturalist may apply to them, are but comparatively slight 

 modifications, founded on developement or addition of certain parts, 

 which do not change the essence of the plan." Of these forms the 

 mollusca furnish the second, of which the essential character is de- 

 rived from the peculiar arrangement of the nervous system, consist- 

 ing of some ganglions scattered as it were irregularly through the 

 body, and from each of which nerves radiate to its various organs. 

 As there is no skeleton, so the muscles are attached to the skin. 



