252 THE NATURAL HISTORY OF 



CLASS.— CRUSTACEA. 



This name, by which this class is distinguished, derives its 

 origin from Crusta, a crust, or shell, because the animals 

 have a covering of this kind. The animals themselves are 

 familiarly known under the name of crabs, lobsters, shrimps, 

 prawns, centipedes, &c. This were deemed by the. ancients 

 as a sub-class of fishes, connecting the true fish with the 

 testaceous Vermes (mollusca) ; and this opinion prevailed, 

 with very little variation, as recent as the time of Linnaeus ; 

 who, in the great revolution which he effected in every part 

 of zoology, separated the Crustacea from fishes and worms, 

 and placed them with insects. After him, our industrious 

 countryman, Pennant, appears to be the first who separated 

 the Crustacea from insects He has, however, neglected to 

 inform us his reason for this change, which renders it rather 

 an innovation than a reform, and deprives him of any claim 

 of priority which he otherwise might have deserved. lie 

 appears to have been rather influenced by caprice than by 

 any conviction of the correctness of his principles, and on 

 these grounds I shall not farther insist upon his claims. 



The illustrious French zoologists, Baron Cuvier, Lamarck, 

 J^treille, and Dumeril, separated the Crustacea from the 

 insecta, abandoning all the former opinions prevalent upon 

 the subject. How far they may have been correct, in re- 

 jecting the doctrines sanctioned by many men of eminence, 

 remains to be ascertained. Much caution is necessary in the 

 examination of innovations, and the utmost impartiality 

 should be used. It is true that animals may have a de- 

 cided resemblance in their external characters, whilst their 

 internal structure is totally different. This has been the case 

 with the classes in question, although it appears to me as 

 very absurd to have placed together animals so very differ- 



