ON ANNELIDA. 61 



in the chetopoda, unless we may consider as such, to a certain 

 point, the cirri of the appendages, when any exist, and espe- 

 cially the tentacula, and the tentacular cirri. Their structure 

 does not appear to differ from that of the general envelope, 

 only they are filled with a substance, which by the action of 

 alcohol, sometimes coagulates incompletely, and is divided 

 into fragments, more or less regular, corresponding to the 

 folds of the envelope, which sometimes gives them the ap- 

 pearance of being articulated. They are sometimes, however, 

 really composed of globular articulations, regular, so as to be 

 completely moniliform, as may be well observed in the species 

 of nereides, which constitute the genus Syllis of M. Savigny. 



As to the black points, or spots, which we have said exist 

 at the upper part of the cephalic rings, and which are pretty 

 generally regarded as eyes, they are evidently formed, each 

 by a small flatted globule of a black colour, and lodged in a 

 particular excavation of the dorsal muscular band, interposed 

 between it and the skin, which appears more thin and trans- 

 parent in this place than elsewhere. 



The locomotive apparatus is essentially composed of the 

 subcutaneous muscular stratum and the appendages, espe- 

 cially the setse which enter into their composition. 



The sub-cutaneous muscular stratum, only more thick un- 

 derneath, and on the sides than above, exists through the 

 whole extent of the body, and forms the greatest portion of 

 its investing sheath. It is essentially composed of longitu- 

 dinal fibres, divided into superior, lateral, and inferior fasci- 

 culi, each separated into two parts, by dorsal, ventral, and 

 lateral lines. These fibres, however, are not extended without 

 interruption, from one extremity of the animal to the other ; but 

 they terminate successively, at least in part, opposite to a vari- 

 able number of rings anterior to that from which they have 

 issued ; but there is no more adherence to the skin in one place 

 than in the other. Thus, in the common nereides, the two dorsal 



