History of Conchuloijy. 



•261 



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 those im- 

 portant 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 Cephalopodes bear their feet and arms like 

 a coronet round the summit of the head ; the Pteropodes swim in 

 their native seas by fin-like oars ; and the Gasteropodes 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 Acephales, because it is strikingly distinguished 

 by the want of head and amorphous form of its constituents ; the 

 Brachiopodes are equally acephalous, but near the mouth they have 

 two fringed fleshy organs which simulate feet ; and the Cirropodes 

 have several pairs of subarticulated fringed feet, in addition to a multi- 

 valved shell of a peculiar construction. The orders of these classes, 

 when the class admits of further subdivision, rest upon distinct dif- 

 ferences in the structure and position of the branchiae 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 locali- 

 ty and wants, it is scarcely possible to conceive that a happier choice 

 could have been made. 



It were unsuitable to our purpose to explain at greater length the 

 Cuvierian system. Enough has been said to show its vast superiori- 

 ty to all that had preceded it ; and 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 improved and increased, the definitions have been 

 rendered more technical and precise, but every method which has fol- 

 lowed, both in its outline and main features, are merely modifications, 

 and very slight ones, of Cuvier's. He always regarded his labours in 

 this field with peculiar satisfaction, and watched their offspring with 

 some degree of jealousy, unwilling that the parentage should be either 

 doubtful or divided. " It is well known," he says, " how much care 

 and time I have devoted to the anatomy of the mollusca in general, 



* Memoirs of Cuvier by Mrs Lee, p. 107-9. 

 VOL. II. NO. 9. S 



