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 tilled 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 setas 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 
