BOOK EIGHTH. 



ANNELIDES. 



CLASSIFICATION. 



§ 142. . 



The Annelides are distinguished from all other worms by their ventral, 

 ganglionic cord, and by their annulated body, at the two extremities of 

 which there is a mouth and anus. They resemble the Arthropoda, but at 

 the same time differ from them in having a completely closed vascular sys- 

 tem, and in wanting articulated, locomotive organs. The epithelium of 

 their body is not ciliated except where it covers the external branchiae. 



The Nemertini, which have hitherto been classed among the Turbellaria, 

 belong more properly to the Annelides, since their body is more or less dis- 

 tinctly articulated, and its parenchyma closely resembles that of the Hiru- 

 dinei. Moreover, the power which many of them have to divide sponta- 

 neously into many segments, is another affinity with various Annelides. It 

 will therefore appear i^roper to unite the Nemertini with the other Anne- 

 lides in the following manner : *^^ 



ORDER I. APODES. 



Body without bristles. 



SUB-ORDER I. NEMERTINI. 



Posterior extremity of body without a sucker j cephalic extremity often 

 provided with lateral respiratory fossae. 



1 Since KoUiker (Verhandl. d. Schweiz. naturf. visit at Trieste in 1847, been convinced that 



Gesellsch. zu Chur. 1844, p. 89) and Quatre- these animals should be classed among the Tur- 



fages (Ann. d. Sc. Nat. VI. 1846, p. 17o) have bellaria, and that they especially deserve this namo 



published their researches on the anatomy of since their entire bod^ is covered with very dia- 



the Nemerthii, I have, also, during my last tinct vibratile cilia. — Additional note. 



