THE ARCTIC CRUSTACEA. 253 



ent, and this was too frequently done by Linnaeus. The 

 most common observer would ridicule the idea that lobsters 

 and crabs were insects! Yet Linnaeus, and many specimen 

 collectors of the present day, either from habit, or a vene- 

 ration for Linnaeus, still consider them as a branch of Ento- 

 mology ; and, as they both agree in having articulated limbs 

 and antennas, they are admitted by many British Entomo- 

 logists into their cabinets as genuine insects, totally dis- 

 regarding their internal structure, economy, and external 

 appearance. 



I shall now describe the distinctive characters of the 

 Crustacea, as laid down by Cuvier, Dumeril, Latreil'e, and 

 Lamarck. It appears that they agree with insects in hav- 

 ing in common with them articulated limbs and antennae. 

 The Crustacea respire by gills like the molluscae, and have 

 generally four antennae or horns, and often six mandibles 

 or jaws; likewise a heart similar to the molluscae. They 

 undergo little or no transformation, and, lastly, they breed 

 more than once. 



Such are the remarkable characters of this class, which 

 appears to warrant a situation by itself. Indeed Linnaeus 

 himself, with that clearness and accuracy which distinguished 

 his general views in every department of Natural History, 

 has laid the foundation of those recent changes effected by 

 the foreign zoologists. That great man has taught us to 

 consider the internal organization " A natural, certain, 

 unerring guide in the classification of animals." The 

 changes thus effected will no doubt meet the views of all 

 those who are competent to duly appreciate the true princi- 

 ples that should regulate every philosophical arrangement. 

 The following are the characters of the Class Crustacea. 



o 



Anatomical Character. 



Heart single; branchiae or gills for respiration ; no verte- 

 brae ; spinal marrow with many knots or ganglia ; muscles 

 for moving the feet. 



