for a time at Caen in Normandy. His sojourn on the borders of the sea induced him, already an enthusiast in natural history, to study marine animals, more especially the mollusca, and the anatomies of them, which he now made, conducted him to the development of his great views on the whole of the animal kingdom. With unwearied zeal he collected the materials which were at no distant date to become the basis of a classification which run through all its details in a harmonious parallelism with the development 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 Linnæan 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 want of constancy was added the fundamental defect of its inappreciable 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 kingdom, 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 principal 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 mo

Limnica.

Family 11. Mollusks with a single siphon and a foot.-Genera-Loripes, Family I. Mollusks with a single siphon.-Genera-Chimæra, Callitriche. Family Iv. Mollusks with a single abdominal siphon and no foot.-Genus

Argus.

Family v. Mollusks without a siphon but with a foot.-Genus-Axinea. Family vi. Mollusks without a siphon and without a foot.-Genera—Daphne, Peloris, Echion, Criopus.

difications, founded on development 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 derived from the peculiar arrangement of the nervous system, consisting 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, which forms a soft contractile envelope protected, in many species, by a shell. The greater number possess the senses of taste and sight, but the last is often wanting. "Only one family can boast of the organ of hearing; they have always a complete system of circulation, and organs peculiarly adapted to respiration; those of digestion and secretion are nearly as complicated as the same organs in vertebrated animals.”* The sub-kingdom, characterized and limited by these important features, is next divided into six classes, the characters of which are mostly derived from the organs of locomotion or others not less influential. Thus the Cephalopods bear their feet and arms like a coronet round the summit of the head; the Pteropods swim in their native seas by fin-like oars; and the Gasteropods crawl on the belly by means of a flat disk or sole. Reaching now tribes among whom the organs of motion are less developed, and accordingly less influential on their manners, Cuvier resorts to others. Thus the fourth class is named Acéphales, because it is strikingly distinguished by the want of head and amorphous form of its constituents; the Brachiopods are equally acephalous, but near the mouth they have two fringed fleshy organs which simulate feet; and the Cirrhopods have several pairs of subarticulated fringed feet, in addition to a multivalved shell of a peculiar construction. The orders of these classes, when the class admits of further subdivision, rest upon distinct differences in the structure and position of the branchiæ or respiratory organs; and when we reflect a moment on the paramount necessity of these to the animal, and their necessary co-adaptation to its locality and wants, it is scarcely possible to conceive that a happier choice could have been made.

We have already explained at sufficient length the Cuvierian system; and enough has been now said to show its vast superiority to all that had preceded it. The solidity of its basis is proved by the fact that the numerous recent discoveries in this department have not shaken it, or altered its principles. The lower divisions and sections have been im

* Memoirs of Cuvier by Mrs. Lee, p. 107-109.

proved and increased, the definitions have been rendered more technical and precise, but every method which has followed, both in its outline and main features, are modifications, and often very slight ones, of Cuvier's. "Multa fiunt eadem, sed aliter;" and the assent of M. Sander Rang to this decision, you may consider as a confirmation of its truth. This excellent naturalist says, "Ce qui fait bien connaître l'excellence de cette distribution, c'est qu'elle n'a point paru un seul instant insuffisante aux progrès de la science et aux nombreuses découvertes qui ont été faites dans ces derniers temps, et qu'elle n'a pu être avantageusement remplacée par celles qui ont été imaginées depuis. Il est même à remarquer que lorsque des naturalistes ont cherché à en créer de nouvelles, ils n'ont fait à peu près que changer la nomenclature; ou bien ils ont adopté une nouvelle série de caractères pour désigner les mêmes classes et les mêmes ordres, ou, enfin, changé entre elles les différentes acceptions des mots de classe, d'ordre, etc., de sorte que les mêmes animaux se sont encore, à peu de chose près, groupés comme auparavant.'

*

* Manuel des Mollusques, p. 18.

522

THE

LETTER XXVII.

HISTORY OF SYSTEMS OF CONCHOLOGY FROM THE PUBLICATION OF CUVIER'S SYSTEM TO ITS COMPLETION.

I HAVE, in my last letter, sketched rather than written the history of Conchology from its first origin to the end of the last century; but I must trace its future progress with a more tedious pen, and travel, moreover, with a guide through its cross and reticulated byepaths. For the names which claim a place in this history are many, and being often those of contemporaneous men, I might find a difficulty in assigning each his place, the works of many of them being placed far beyond my reach by the expensive manner in which they have been published; nor does my library furnish the various editions even of those which have been most influential. I shall, therefore, assume Deshayes for my guide; * who, so far as my means enable me to judge, is both an honest and a learned one.

It was in 1798 that Cuvier published this his first arrange

*Traité Elémentaire de Conchyliologie, avec l'application de cette Science à la Géognosie. Par G. P. Deshayes, 2 vols. 8vo. 1839. This work, which I cannot too highly commend, is indispensably necessary to the Conchologist. It is not yet completed.

Murex, Voluta,

D. shell turbinate, the aper- Strombus, Oliva,

D. A. conchiferous and with

Solen, Pholas,

a foot, the valves equal, the
shell gaping at both ends,
the lobes of the mantle close Mya, Teredo.

in front

E. A. conchiferous and apod

ous, furnished with two Terebratula, Orbicula.
fleshy ciliated spiral ten-Lingula.

tacula

E. A. testaceous, furnished.

with a number of jointed Anatifa, Balanus.

and ciliated tentacula ar

ranged in pairs .

There are, you perceive, three primary sections of equal value, and their characteristic names are for the first time introduced into science. In preceding systems the Cephalopods were considered to be constituents of the order of soft worms, while the Nautilus and Argonauta were members of the order Testacea. The division of the Gasteropods into two subsections from the absence or presence of a shell was not a happy one; and the unnatural result was to remove the Limax far away from its near relative the Helix. The claims of the Thalides and Lernæa to a place in this order were subsequently proved to be unfounded. The arrangement of the testaceous Gasteropods is borrowed partly from Linnæus and partly from Adanson; and Poli professedly supplied the characters on which Cuvier distributed the Bivalves into their families. He was more original and acute when he embodied with them the naked Acephales, although it is probable that he may have found the hint of their