PRIMARY DIVISIONS OF ANNULOSA. 7 



intimated, constitute one : they are all aquatic, worm- 

 like animals, known by having usually red instead of white 

 blood : while their bodies, from being articulated, at 

 once prevent them from being confounded either with 

 the slug-like Mollusca or the Polypes. The next great 

 division which shows an evident resemblance to the last, 

 is the intestinal worms ; being of the most simple struc- 

 ture, but the greatest part of which exhibit, although 

 but faintly, the annulose jointed body, which at once 

 decides that their structure is truly annulose. The 

 types of these are chiefly composed of the Tcenio'idea 

 of Cuvier, but there are several other forms among the 

 Entozoa of Rudolphi, which will ultimately be referred 

 to this type, an assemblage which appears to us in very 

 great confusion. The third aberrant division is dis- 

 tinguished from the two last, by having five pair of 

 feet, branching off into articulated fringed cirrhi : these 

 are the Cirrhipedes, or barnacles. It was reserved for 

 a countryman of our own, Mr. Thompson, to make 

 known the extraordinary fact, that these animals undergo 

 a metamorphosis ; a discovery which at once removes all 

 doubt on their natural station. These appear to us 

 the three great aberrant groups of the Annulosa. The 

 general reader will have a very good idea of them, by 

 looking to an earth-worm as an example of the Anne- 

 lides; a tape-worm as representing the class Vermes ; 

 and a barnacle as representing that of the Cirrhipedes. 

 These three classes unite themselves, in all probability, 

 into a circle of their own ; for it is a remarkable fact, 

 that Cuvier places the Cirrhipedes immediately conti- 

 guous to the Annelides, thereby tacitly confirming the 

 position we have so frequently advanced, that there is a 

 tendency in all aberrant groups to unite into one circle. 

 Leaving, however, these imperfect Annulosa, we next 

 come to those whose bodies are provided with distinctly 

 formed legs and jointed feet, and of whose annulose 

 structure there can be no doubt. These, we consider, 

 after the example of Aristotle and Linnaeus, as naturally 



