REPORT ON ZOOLOGY. 187 



of the classes referred by Cuvier to this type of structure sepa- 

 rately. To these I shall add Dr. Leach's class of Myriapoda. 



1, Annelida. — This class was established by Cuvier iu 1802. 

 Lamarck, who adopted it from him, was, however, the first to 

 assign to it its present name. The animals which it includes, al- 

 though possessing great intei-est fi'om the circumstance of their 

 forming the passage from the Annulose to the Vertebrate type, 

 have been comparatively but little studied, and have received the 

 attention of only a few naturalists. It is principally to Cuvier, 

 Savigny, Blainville, and to the more recent researches of Au- 

 douin and Edwards, that we are indebted for what knowledge 

 we have respecting them as a class. Cuvier more especially ex- 

 amined their internal organization. His arrangement, in both 

 editions of the R^gne Animal, is grounded upon the respiratory 

 organs, which furnish him with the characters of three groups, 

 which he terms orders : (1.) Tubicoles, in which the branchiae 

 are in the form of tufts attached to the head or anterior part of 

 the body, generally inhabiting shelly tubes ; (2.) Dorsibranches, 

 in which they are arranged down the back or along the sides of 

 the body; and (3.) Abranches, in which there are no distinct 

 branchiae visible. Savigny, whose valuable memoirs on these 

 animals * are inserted in the great French work on Egypt, paid 

 more attention to their external structure. He particularly 

 studied the conformation of those elastic and often brilliant 

 metallic-like seta;, which in a great number of genera serve as 

 organs of motion. He also entered into a detailed examination of 

 the jaws, antennae, branchiae, and the membranaceous append- 

 ages attached to the several articulations. His arrangement of 

 this class is very different from Cuvier's. He divides it into 

 five orders : (1.) Nereidi^es, comprising such genei'a as have re- 

 tractile feet furnished with setae, a distinct head, and a mouth in 

 the form of a proboscis, generally armed with jaws ; (2.) Ser- 

 piilees, in which there are also feet furnished with setae, some 

 of these being hooked, but no distinct head ; (3.) Lombricines, 

 M'ithout feet or distinct head, but nevertheless furnished with 

 small setae ; (4.) Hirudinees, without distinct head, feet, or setae, 

 but with a mouth in the form of a sucker; (5.) The last order, 

 of which he has not treated, he has left without a name. The 

 result of Blainville's researches into the structure of these ani- 

 mals, which form his class Chetopodes, will be found in the 



* Recherches pour servir a la Classification des Annelides ; and Tableau 

 si/slemaligue tie la Classe des Awielides. The first of these memoirs was pre- 

 sented to the Royal Academy of Sciences in 1817. An analysis of them both 

 will be found in Latreille's Report, published in the il/m. c^k JV/?(5e!(7«, tom. vi. 

 p. 93. 



